We investigated changes in calling behavior of individual male Bufo woodhousei in response to playback of natural and synthetic acoustic stimuli. Males lowered their call rates and avoided acoustic overlap with all stimuli centered at 1.4 kHz; only a high frequency (3.8 kHz) stimulus was ineffective. Even filtered noise centered at 1.4 kHz was an effective inhibitor of calling activity. Variation in rate of amplitude modulation of acoustic stimuli had no apparent effect on male calling behavior. These results are discussed in relation to species recognition in bufonids, and acoustic competition between male anurans in general.