An examination of four specimens of the common caiman, Caiman crocodilus (L.), from small lakes ("lagunas") in the surroundings of Boca de Anaro on the Suripa River, State of Barinas, Venezuela revealed the presence of two nematode species, Brevimulticaecum baylisi (Travassos, 1933) and Micropleura vazi Travassos, 1933. The finding of the latter species represents its first record from Venezuela and from the Orinoco River drainage system. A detailed study of their morphology, including SEM, made it possible to establish some new, taxonomically important morphological features of these species (e.g., the presence of cervical alae and the exact number and arrangement of male caudal papillae in B. baylisi, the number and arrangement of cephalic papillae and the structure of cuticular ornamentation in M. vazi). Brevimulticaecum sp. infective larvae reported by Moravec et al. (1997) from fishes originating from the same locality as the caimans are now considered to belong to B. baylisi.