Mice, similarly to some other rodent species, communicate with specialized sounds in the ultrasonic range called ultrasonic vocalizations (USV). Evaluation of this behavioral activity enables estimation of the social interactions in animal models of autistic spectrum disorders (ASD). Because transgenic mouse models are generated, in most cases, on the mixed 129SV/ C57BL6 genetic background, we were interested if parameters that characterize USV differ between these two mouse strains. In addition, we wanted to compare these strains with the BALB/c line. In order to analyze USV, we applied the standard isolation test to newborn animals and compared standard parameters. Obtained results indicate clear differences between the 129SV and C57BL6 strains in respect to all analyzed USV parameters. Both strains behave also differently when compared with the BALB/c strain. For this reason in experiments utilizing transgenic animals, contribution of various genetic backgrounds has to be carefully considered.