A vocalization of the ringtailed lemur (Lemur catta) was examined for individual differences according to several temporal- and frequency-dependent variables. Vocalizations were tape recorded at the Duke University Primate Center (Durham, NC) and spectrographically analyzed. Significant differences were found in pair-wise comparisons of call structure among the study subjects, thus providing the physical basis for individual discrimination. A separate analysis comparing degree of kinship and vocal similarity revealed a positive but nonsignificant correlation between these two variables. This study represents an initial examination of vocal individuality in prosimian primates.