Many researchers have studied the population of individuals with mild mental retardation (MIMR) as if it is a clear entity. Few researchers have investigated potential subtypes within the MIMR population. The purpose of the present study was to investigate which subtypes can be identified on the basis of intellectual, adaptive and behavioral functioning. Seventy-three individuals with MIMR were assessed on measures of intellectual, adaptive and behavioral functioning. An agglomerative hierarchical cluster-analytic technique was used to define potential subgroups with characteristic behavioral patterns. Four subtypes were identified. The behavioral patterns are described and implications for assessment are discussed. (Contains 5 figures and 5 tables.)