Vocalization patterns of two groups of captive Francois' langurs (Presbytis francoisi) were studied between August 1989 and June 1990. During the 11 months of observation, 109 hours of vocalization recordings were made at Metro Washington Park Zoo, Portland, and the San Diego Zoo, San Diego. Based on the behavioral observations and the vocalization recordings, two categories of vocalization types are described. Type I consists of 20 basic patterns including infant vocalizations and a vocalization recorded by other observers. Type II consists of 3 patterns related to stereotypic behavior and possible stress under captive conditions. Physical characteristics and the context of behavior for each call type are described. Spectrograms are given for all call types except the loud call. Among the calls recorded, whistle vocalizations of infants are the longest in duration. Comparison of vocalization patterns of P. francoisi to those of other species of the genus Presbytis revealed similarities in behavior and context among some call types in the species of P. entellus and P. johnii. / Graduation date: 1992