Characteristics which distinguished patients at federally funded rural community mental health centers in 1971 from those at part rural and non-rural centers were explored. Variables examined were: demographic composition (age, color, and sex), socioeconomic characteristics (annual family income, educational attainment, and marital status), primary diagnosis, previous mental health care, and referrals to and from centers. The 295 centers were classified according to: (1) rural--a center serving a catchment area consisting exclusively of rural counties; (2) non-rural--a center serving a catchment area containing no rural county; and (3) part rural--a center serving a mixed catchment area with one or more rural and one or more non-rural counties. Demographically, more rural patient additions were in the dependency age groups, fewer were black, and more were female than were non-rural additions. Rural center additions were characterized by more lower income persons, more persons with low educational attainment, and more married but fewer never married, separated or divorced persons than were part rural and non-rural additions. More rural additions had received previous mental health care. Differentials by rurality in referral disposition upon discontinuation from centers and in diagnosis were relatively minor. (NQ)