An analysis was conducted of plant parasitic nematodes occurring in banana (Musa AAA) plantations in Costa Rica from 1995 to 1999. Nematodes were recovered on 0.038-mm-pore sieves after macerating 25 g of fresh roots in a blender. Data were subjected to frequency analysis and the absolute frequency was calculated for each genus. Four genera of plant parasitic nematodes were detected. Radopholus similis was the most abundant nematode accounting for 82 to 86% of the overall root population throughout the survey. From a total of 60,032 root samples, 58,297 (97%) contained R. similis, 33,504 (56%) Helicotylenchus spp., 30,227 (50%) Meloidogyne spp., and 8,674 (13%) Pratylenchus spp. Only on 355 (0.6%) samples, were any of those nematodes undetected. High population densities of R. similis were found in all years, months, and counties. Additional studies are necessary to verify if this relative importance coincides with root damage and economic threshold.