Eight to ten precipitin bands were formed in a double immunodiffusion system comparing antigens of adult females of Meloidogyne incognita and M. arenaria. Most of the precipitin bands, based on band position and coalescence, were common to both species. Antiserum specific for M. incognita was prepared by cross absorption. Two populations of M. incognita were serologically identical, whereas two populations of M. arenaria differed slightly with respect to one weak precipitin band.