A location (area 10 km²) of the agile frog (Rana dalmatina Fitz. in Bonaparte) in a southwest part of the Sandomierz Valley (southern Poland), was surveyed during 4 breeding seasons (1999–2002). Eighteen breeding sites of brown frogs were inspected for their characteristics, presence and numbers of egg-batches, and time of egg deposition. Breeding sites were typically temporary, small, and shallow waters (area 5–30 m², depth <50 cm). The agile frog was found to co-occur only with the common frog (Rana temporaria L.) in most of the sites. Based on the number of egg-batches, the agile frog was more numerous (total of 315 batches in year 2002) than the common frog (163). Over the four years of the study, there were no significant fluctuations in the numbers of eggs. The two species did not differ significantly in their choice of the habitats, except for the sites with low water pH, used predominantly by the agile frog. Habitat niche overlap was high (Pianka’s O = 0.86). In the acid peat bogs (water pH about 4.5) most of the eggs degenerated.