The splenic artery of four mammals-pig, greyhound, rhesus macaque, and olive baboon-was studied to determine its tortuosity and pattern of convolutions. The results were compared to those previously gathered in humans. It was found that the isolated cadaveric arteries showed a noticeable species variation in mean index of tortuosity. In the pig and dog, the artery was nearly straight throughout its length, with a very low index of tortuosity, not significantly different in the two species ( P > 0.1). T h e artery was significantly more tortuous in the rhesus macaque and baboon than in both pig and dog, (Ps < 0.001), with a single large convolution present in the proximal one-third. In humans, the artery is commonly tortuous throughout its length and is significantly more tortuous than in the pig and dog ( P < 0.001), but not significantly more tortuous than in the baboon (P > 0.1) and only just significantly more so than in the rhesus macaque (0.02 < P < 0.05). T h e speculation that the tortuosity of the artery may be related to habitual posture, being less in the pronograde pig and dog than in the partly orthograde rhesus macaque and baboon, is not supported by results in the wholly orthograde human.