1. Lemurs (Lemur catta) and six groups of monkeys - three groups of Old World and three of New World monkeys were compared by means of gross observations in laboratory cages. 2. The profile of scores for any one animal was unambiguously diagnostic of its species. 3. Rhesus and apella monkeys specialized in manipulating objects, stumptail monkeys in social grooming, squirrel monkeys in self manipulation and woolly monkeys in vocalizing. 4. Lemurs were not as socially oriented as monkeys and spent most of their time in visual survey or looking at social objects. 5. Results were discussed in terms of implications for laboratory studies that are based largely on one nonhuman primate (Macaca mulata).