The ecology and social behavior of the St. Kitts green monkey were investigated for a total of 77 days and 128 h during the summers of 1969 and 1970. This report deals with the ecology and population dynamics of the St. Kitts population. A discussion of the diet, locomotor patterns, the daily routine, and territorial behavior is also included. Significant variations within the St. Kitts population and between this population and African species are noted. Suggestions for a future course of research are offered.