1. The sympatric, genetically compatible treefrogs,Hyla chrysoscelis andH. femoralis, were artificially crossed (reciprocally) and the F1 hybrid progeny raised to sexual maturity in the laboratory. The calls of males and selective phonotaxis of females were studied. 2. Male hybrids began calling about seven months after the cross was made. The temporal properties of the vocalizations were intermediate, more similar to one or the other of the calls of the parental species, or unique to hybrids. Pulse period (pulse-repetition rate) was the most stereotyped temporal property and was more similar to that in the calls ofH. femoralis thanH. chrysoscelis. Dominant frequency of the calls of hybrids and both parental species was typically between 2 and 3 kHz. 3. In two-stimulus playback experiments, F1 female hybrids were selectively attracted to hybrid calls in preference to those ofH. chrysoscelis. Females did not prefer hybrid calls over those ofH. femoralis, probably because of an overlap in pulse period and a significant difference in the total amount of acoustic stimulation. When these factors were eliminated or reduced by presentation of synthetic calls, female hybrids chose a stimulus with a pulse period typical of hybrids in preference to a call with a pulse period typical ofH. femoralis. 4. There were no differences in the call structure nor in the selective phonotaxis of F1 hybrids of the reciprocal crosses, thus indicating that sex-link-age and maternal effects are probably not involved in the genetic specification of the acoustic communication system. 5. The behavioral coupling (with respect to pulse period) demonstrated in this study and in crickets is consistent with the predictions of the ‘genetic coupling’ hypothesis, which postulates that both signal generating and recognition mechanisms share common circuitry specified by the same genes. The results of these behavioral studies are sufficiently encouraging to warrant neurophysiological, anatomical and genetic experiments that can provide direct tests of the hypothesis.