Repeatability, that is the intra-class correlation coefficient (Sokal & Rohlf 1981), describes the degree to which variation within individuals contributes to the total variation in a group of individuals. In this study the repeatability for several parameters of the tonal and the drumming sounds emitted by breeding males of Padogobius martensii was measured to examine (1) which parameters of the sounds were more repeatable (i.e. stereotyped), (2) the contribution of temperature and male size to between-male variation in sound parameters, and (3) the potentiality for individual assessment/recognition by acoustical means in this species. Sounds were collected from single bouts of calling by 16 males differing in body size and ambient water temperature. All the sound parameters examined showed a remarkable inter-male variability. Water temperature explained most of between-male variation in the properties of the tonal sound, while body size was the main factor explaining the between-male variation in the properties of the drumming sound. After temperature control, however, the two types of sound showed a similar pattern of variation in the acoustic properties. Parameters of the tonal sound were less repeatable than their counterparts in the drumming sound. In general, high repeatability in a sound parameter was associated with a larger contribution of male size to the between-male variation in that property (after correction for temperature). Because of higher repeatability and stronger relationship with male size, the drumming sound appears to be adapted to convey information about the quality of the emitter (assessment signal).