SYNOPSIS. Except for lions and cheetahs, members of family Felidae exhibit spatially and temporally dispersed social systems. However, this solitary existence does not preclude possession of a rich repertoire of communication signals. While patterns of communication have been examined in a number of the larger cats (e.g., lions, cheetahs, tigers), those of the smaller cats (<20 kg) remain virtually unstudied. The purpose of this study was to examine behavior in the smaller members of the Family Felidae to determine the level of behavioral uniformity within the family and to ascertain whether systematic behavioral observations could be used as an effective bioassay to monitor reproduction. A comparative examination of the occurrence and rate of scent marking, social behavior (especially behaviors associated with copulation), and other reproductive parameters was made in 20 species of captive, small felids. In general, small felids exhibited remarkable uniformity in their behavioral repertoire, both with respect to scent-marking and social behaviors. While the frequency of social behaviors differed among species, their appearance and general order of occurrence was similar. This was especially apparent with regard to the copulatory sequence. Detectable behavioral changes occurred in association with reproduction, supporting the concept of using systematic behavioral observations as a viable, non-invasive assay for monitoring reproductive activity. Reproductively active felids scent marked more frequently than reproductively inactive cats. However, no single scent-marking behavior was a good indicator of reproductive activity. Rather, the relative change in rates of behaviors over time was a better indicator of reproduction. As with scent-marking behaviors, a change in the relative rates of some social behaviors was the most reliable indicator of reproductive activity. Comparative behavioral data also show promise for understanding the phylogenetic relationships of three proposed lineages within the family Felidae (Panthera, ocelot, and domestic cat).