We employed a Bayesian statistical approach to examine female preferences in the Neotropical frog Physalaemus pustulosus for the temporal relationship of the two parts of the conspecific advertisement call. The male advertisement call consists of a 'whine', which is necessary for species recognition, followed immediately by one or more 'chucks', which make the whine more attractive to females. We conducted 42 two-choice experiments with a total of 840 individual tests to compare the attractiveness of a whine with a chuck in a variety of positions relative to the start of the whine against a normal whine or against a normal whine/chuck. Females have a bimodal preference function for chuck position. Chucks placed in a variety of positions after the whine (including the position of a chuck in a normal call) were generally as attractive as a normal whine/chuck. Chucks placed before the whine were generally more attractive than a whine alone, and in some positions as attractive as the normal whine/chuck. Chucks overlapping the end of the whine make the call more attractive than a whine alone, but not as attractive as a normal whine/chuck, while chucks overlapping an initial portion of the whine beginning 50 ms into it are ignored; previous work (Wilczynski et al. 1995, Animal Behaviour, 49, 911-929) indicates this region to be critical for species recognition. These results suggest that female P. pustulosus have preferences for the temporal relationship of the two parts of the conspecific male advertisement call that far exceed the vocal signals produced by males, and that male calls have evolved calls to exploit one peak of this function. Copyright 1999 The Association for the Study of Animal Behaviour.