Measurement and comparison of mating calls in anuran amphibians is desirable because differences in call are important mechanisms that help to prevent free interbreeding of closely related species. Calls have been recorded and analyzed on a Sona‐Graph for some 27 species representing 10 genera of amphibians. Calls vary individually in natural populations; they vary geographically within species populations; and they differ between species. Closely related species which occur together differ conspicuously from one another in at least one or two variables, such as emphasized frequency or duration.