The catalytic activity of phospholipase A2 (PLA2) was measured in serum samples from 32 crocodiles in Thailand and Australia by a method using 14C-oleic acid-labelled autoclaved Escherichia coli membranes as a substrate. The highest PLA2 activity was measured in the serum of Crocodylus siamensis (n = 9, mean ± SD), 13.3 ± 3.1 U/l followed by hybrid C. siamensis × C. porosus (n = 6), 10.4 ± 8.7 U/l and Crocodylus porosus (n = 17), 4.3 ± 3.0 U/l. The difference between C. siamensis and C. porosus was highly significant (P < 0.001). The gender of the animals and the geographical location of the crocodile farms were not significant variables affecting serum PLA2 levels. It was concluded that PLA2 is present in crocodilian serum and may have an antimicrobial role.