The thumb is very important for the hand function mainly by its oposition capacity. Their arteries are branches of two important antebrachial arteries, radial and ulnar. With the purpose to know more details over the formation of the proper palmar digital arteries of the thumb, we studied 60 hands from adult cadavers of both sexes, all of brazilian origin. Their arteries were injected with latex neoprene. The princeps pollicis artery was found in 59 cases (98.3%) and it originated from the radial artery or one of its branches after this one have passed through the first interosseous space in 54 (90%); this artery arose before the radial artery or one of its branches have passed through the mentioned space above in 5 (8.3 %), in these cases the princeps pollicis artery ran dorsal and superficially. The radial proper palmar digital artery of the thumb was formed by: one branch of the princeps pollicis artery in 25 cases (44.6%); by one branch of the last mentioned artery plus a branch from the superficial palmar arch in 14 (25%); by one branch from the princeps pollicis artery plus one branch from the median artery in 8 (14.3%). The ulnar proper palmar digital artery of the thumb was formed by: one branch from the princeps pollicis artery plus one branch from the superficial palmar arch in 40 cases (71.4%); by one branch of the princeps pollicis artery plus one branch from the median artery in 6 (10.7%); by one branch from the princeps pollicis artery plus one branch from the superficial palmar branch of the radial artery in 4 (7.1%). Thumb irrigation is mainly subject to the princeps pollicis artery which receive frequently branches from the superficial palmar arteries