This report presents an analysis of the vocal repertoire of howler monkeys (Alouatta palliata) observed during a field study in southwestern Panama. 26 types of vocalizations were identified and described, and sonagrams are presented for 21 of them. The vocal repertoire contained many nondiscrete calls that graded continuously into each other, and all of the calls appeared to fit into 5 or 6 broad families. A tape recording of the vocalizations described in this study is available.