The projective Hand Test (Wagner, 1962/1983) was administered to 17 older adults with a dual diagnosis (mental retardation existing concurrently with some form of mental illness) residing in a Midwestern institution for the mentally retarded. Each of these individuals was matched with another resident in the same institution with a single diagnosis of mental retardation on the variables of age, sex, and level of mental retardation to determine differences between the groups on the Hand Test. The dual diagnosis group gave significantly more bizarre (BIZ) responses, whereas the single diagnosis group gave more descriptive (DES) responses. It was contended that these two variables accurately reflect the essential difference between dual and single diagnosed mentally retarded individuals.