The reliability of the DSM-III diagnostic system was assessed in a medical long-term care facility population that was recently seen in psychiatric consultation. Six standard rating scales were used to determine interrater agreement for perceiving psychopathology prior to selecting diagnoses. The findings were that six major diagnostic groups could be accurately distinguished from one another: no disorder; organic mental disorders; affective disorders; paranoid disorders; schizophrenia and psychotic disorders not elsewhere classified; and a mixed group of other diagnoses that occurred in low frequency in this study population. The interrater reliability (kappa = 0.64–0.70) was comparable to that found in the general psychiatric population.