Complex-tone (fundamental) frequency discrimination was measured in eight well-trained listeners with moderately severe sensorineural hearing impairments as a function of parametric variations in the rank, number, and sensation level of stimulus components. Results indicate substantial differences in the effects of harmonic content on complex-tone frequency discrimination among hearing-impaired listeners and between hearing-impaired and normal-hearing listeners. Despite large variability among the hearing-impaired subjects, several patterns of results emerged: Performance of two subjects grew worse as harmonic rank increased; performance of three subjects did not change substantially with changes in harmonic rank; and performance of three impaired subjects improved as harmonic rank increased. Performance of all but two subjects was significantly degraded for stimuli containing low-order harmonics. For stimuli containing only high-order harmonics, five subjects showed performance that was comparable to that of normal-hearing subjects, and three showed abnormally poor performance. Performance of impaired subjects generally improved as the number of stimulus components increased. The sensation level of stimulus components influenced the performance of several impaired subjects, but not in a uniform manner. To the extent that complex-tone fundamental-frequency discrimination can be assumed to be a pitch perception task, the present results suggest that, in contrast to normal-hearing subjects, hearing-impaired listeners rely primarily on periodicity cues in the perception of complex-tone pitch.