From February 2005 to September 2007, a total of 490 crocodile sharks Pseudocarcharias kamoharai, caught as by-catch in the swordfish and tuna longline fishery that operates in the tropical western Atlantic Ocean, was studied in regard to their reproductive biology. Maximum observed total lengths (L(T)) were 1220 and 1090 mm for females and males respectively, with a high proportion of the catch being composed of mature specimens. Sexual maturity was attained at 760-810 mm L(T) for males (L(T50) = 800 mm) and 870-980 mm L(T) for females (L(T50) = 916 mm). The size at birth was estimated at 415 mm L(T). Temporal variation in gonad morphology and mass suggests that in this region P. kamoharai, an aplacental viviparous species with oophagy, does not show a well-defined reproductive seasonality, with mating and parturition occurring possibly over an extended period of the year. Mean +/-S.D. fecundity was estimated to be 3.9 (+/- 0.6) pups per reproductive cycle.