Along the transition from AD&D 1st to 2nd Edition to D&D 3rd Edition, the various races of giants have experienced significant power inflation. Going from 1st to 2nd Edition, giants were increased by about +50% Hit Dice. From 2nd to 3rd Edition, they received large Constitution bonuses which approximately double their hit points.
Arguably, the 2nd Edition increase was redundant with this last step -- giants' overall hit point increase now amounts to a tripling, as opposed to most creatures in the Core Rules which saw merely a doubling (in approximate terms). Two other problems present themselves. First, giants' Hit Dice drastically break the "standard hit dice progression" for their size category (see here: monster_abnormal_hd). Second, the relative power of giant opponents in classic AD&D modules becomes somewhat broken compared to the encounters around them (see my conversions for Module G1-3 at ENWorld.org, here: http://enworld.cyberstreet.com/news/modules).
Additionally, there is some evidence that Giant Challenge Ratings as listed are too low. Using a computer program to simulate melee combats, I've found that each type of giant is best matched against an NPC fighter of their listed CR + 4. Interestingly, when simulating my conversions below, the calculated CRs actually come out equal to those listed for the official 3rd ED. giants. (However, I've scaled the CRs below to fit with the official CRs.)
Therefore, for purist GMs who are interested in more closely simulating original AD&D (or clearing up these other problems), I offer the following conversions of giants from 1st Edition sources.
Note: With regard to fire giants, an argument could be made that they should actually be categorized as Huge-size -- inasmuch as they are "squat, resembling huge dwarves", and dwarves qualify as Medium-size even though they are under the minimum height of 4'6" for other Medium-size PC races. I have not done so below, however, and in any case no statistics should change other than the Face/Reach entry.
Note: In the last two sections I have only converted those races for which female and young giants are commonly encountered (i.e., those featured in Module G1-3).
GIANTS (MALE)
Giant, Hill: Large Giant; CR 5; HD 8d8+32; hp 68; Init -1; Spd 30 ft.; AC 16 (hide); Atks huge greatclub +11/+6 (2d6+9), rock +5/+0 (2d6+6); Face/Reach 5x5 ft./10 ft.; SA Rock throwing (40 ft. increment); SQ Rock catching; AL CE; SV Fort +10, Ref +1, Will +2.
Str 23, Dex 8, Con 19, Int 6, Wis 10, Cha 7.
Skills and Feats: Climb +6, Jump +6, Spot +4; Cleave, Power Attack.
Giant, Stone: Large Giant (Earth); CR 6; HD 9d8+36; hp 76; Init +2; Spd 30 ft.; AC 20 (hide); Atks huge greatclub +12/+7 (2d6+10), rock +8/+3 (2d6+7); Face/Reach 5x5 ft./10 ft.; SA Rock throwing (60 ft. increment); SQ Rock catching (+4); AL N; SV Fort +10, Ref +5, Will +3.
Str 25, Dex 15, Con 19, Int 10, Wis 10, Cha 11.
Skills and Feats: Climb +7, Hide -2*, Jump +7, Spot +4; Point Blank Shot, Power Attack.
Giant, Frost: Large Giant (Cold); CR 7; HD 10d8+50; hp 95; Init -1; Spd 40 ft.; AC 17 (chain shirt); Atks huge greataxe +14/+9 (2d8+12), rock +6/+1 (2d6+8); Face/Reach 5x5 ft./10 ft.; SA Rock throwing (40 ft. increment); SQ Rock catching, cold subtype; AL CE; SV Fort +12, Ref +2, Will +3.
Str 27, Dex 9, Con 21, Int 10, Wis 10, Cha 11.
Skills and Feats: Climb +11, Jump +11, Spot +4; Cleave, Great Cleave, Power Attack.
Giant, Fire: Large Giant (Fire); CR 8; HD 11d8+55; hp 104; Init -1; Spd 30 ft.; AC 19 (chainmail); Atks huge greatsword +16/+11 (2d8+13), rock +7/+2 (2d6+9 and 2d6 fire); Face/Reach 5x5 ft./10 ft.; SA Rock throwing (40 ft. increment); SQ Rock catching, fire subtype; AL LE; SV Fort +12, Ref +2, Will +3.
Str 29, Dex 9, Con 21, Int 10, Wis 10, Cha 11.
Skills and Feats: Climb +9, Jump +9, Spot +5; Cleave, Great Cleave, Power Attack.
Giant, Cloud: Huge Giant (Air); CR 9; HD 12d8+72; hp 126; Init +1; Spd 50 ft.; AC 18; Atks gargantuan morningstar +17/+12 (4d6+15), rock +9/+4 (2d8+10); Face/Reach 10x10 ft./15 ft.; SA Rock throwing (50 ft. increment), spell-like abilities; SQ Rock catching, scent; AL NG/NE; SV Fort +14, Ref +5, Will +5.
Str 31, Dex 13, Con 23, Int 12, Wis 12, Cha 13.
Skills and Feats: Climb +14, Jump +14, Listen +7, Spot +8; Alertness, Cleave, Power Attack.
Giant, Storm: Huge Giant (Electricity); CR 10; HD 15d8+90; hp 157; Init +2; Spd 50 ft., swim 40 ft.; AC 20; Atks gargantuan greatsword +20/+15/+10 (4d6+16), gargantuan mighty composite longbow [+11] +11/+6/+1 (2d8+11); Face/Reach 10x10 ft./15 ft.; SA Spell-like abilities; SQ Electricity immunity, rock catching, freedom of movement, water breathing; AL CG; SV Fort +15, Ref +7, Will +8.
Str 33, Dex 14, Con 23, Int 16, Wis 16, Cha 15.
Skills and Feats: Climb +16, Concentration +10, Jump +15, Perform (chant, drama, harp, recorder) +6, Spot +8; Cleave, Great Cleave, Power Attack, Sunder.
GIANTS (FEMALE)
Giant, Hill, Female: Large Giant; CR 4; HD 8d8+16; hp 52; Init -1; Spd 30 ft.; AC 16 (hide); Atks huge greatclub +9/+4 (2d6+6), rock +5/+0 (2d6+4); Face/Reach 5x5 ft./10 ft.; SA Rock throwing (40 ft. increment); SQ Rock catching; AL CE; SV Fort +8, Ref +1, Will +2.
Str 19, Dex 8, Con 15, Int 6, Wis 10, Cha 7.
Skills and Feats: Climb +4, Jump +4, Spot +4; Cleave, Power Attack.
Giant, Frost, Female: Large Giant (Cold); CR 6; HD 10d8+40; hp 85; Init -1; Spd 40 ft.; AC 14 (padded); Atks huge greatclub +13/+8 (2d6+10), rock +6/+1 (2d6+7); Face/Reach 5x5 ft./10 ft.; SA Rock throwing (40 ft. increment); SQ Rock catching, cold subtype; AL CE; SV Fort +11, Ref +2, Will +3.
Str 25, Dex 9, Con 19, Int 10, Wis 10, Cha 11.
Skills and Feats: Climb +12, Jump +12, Spot +4; Cleave, Great Cleave, Power Attack.
Giant, Fire, Female: Large Giant (Fire); CR 7; HD 11d8+44; hp 93; Init -1; Spd 30 ft.; AC 17 (hide); Atks huge greatsword +15/+10 (2d8+12), rock +7/+2 (2d6+8 and 2d6 fire); Face/Reach 5x5 ft./10 ft.; SA Rock throwing (40 ft. increment); SQ Rock catching, fire subtype; AL LE; SV Fort +11, Ref +2, Will +3.
Str 27, Dex 9, Con 19, Int 10, Wis 10, Cha 11.
Skills and Feats: Climb +10, Jump +10, Spot +5; Cleave, Great Cleave, Power Attack.
GIANTS (YOUNG)
Giant, Hill, Young: Medium Giant; CR 1; HD 4d8+8; hp 26; Init +0; Spd 20 ft.; AC 16 (hide); Atks greatclub +5 (1d10+3); AL CE; SV Fort +6, Ref +1, Will +0.
Str 15, Dex 10, Con 15, Int 5, Wis 9, Cha 6.
Skills and Feats: Climb +1, Jump +1, Spot +1; Power Attack.
Giant, Frost, Young: Medium Giant (Cold); CR 2; HD 5d8+15; hp 37; Init +0; Spd 30 ft.; AC 14 (padded); Atks greatclub +7 (1d10+6); SQ Cold subtype; AL CE; SV Fort +7, Ref +1, Will +0.
Str 19, Dex 11, Con 17, Int 9, Wis 9, Cha 10.
Skills and Feats: Climb +7, Jump +7, Spot +2; Cleave, Power Attack.
Giant, Fire, Young: Medium Giant (Fire); CR 2; HD 5d8+15; hp 37; Init +0; Spd 20 ft.; AC 17 (hide); Atks greatclub +8 (1d10+7); SQ Fire subtype; AL LE; SV Fort +7, Ref +1, Will +0.
Str 21, Dex 11, Con 17, Int 9, Wis 9, Cha 10.
Skills and Feats: Climb +5, Jump +5, Spot +2; Cleave, Power Attack.