We presented male tungara frogs, Physalaemus pustulosus, with call-triggered computer-synthesized whines that either did or did not overlap the frogs' own frequency-modulated whines in time. When the stimulus was nonoverlapping, males added a high proportion of chuck notes to their calls. When the stimulus was overlapping, males responded with either no or only small increases in chucking. This suggests they have difficulty detecting whines while vocalizing. When female tungara frogs were given a choice between alternating whines and out-of-phase overlapping whines they did not discriminate. The result with males was similar to that previously obtained with species of frogs that have amplitude-modulated advertisement calls (Schwartz 1987a), the result with females was different. We discuss our findings in relation to peripheral processing of spectral and temporal information in the anuran auditory system.