The present study examines antigenic variability for the human whipworm Trichuris trichiura. Recognition by IgG of somatic antigens of individual worms collected from 3 intensely infected children from Jamaica, West Indies has been investigated by immunoblotting. When probed with 1 plasma sample, significant differences in recognition of 2 selected antigens among worm populations and between male and female worms was observed. In addition, there was evidence for antigenic variability within worm populations at the individual worm level. Such variation may have considerable implications for the development of immunity to parasitic nematodes.