The purpose of this paper was to determine the impact of geriatric medical services on mental state by reviewing all controlled trials of such services. Two computer data bases were searched for relevant articles published from January 1980 to August 1990, and the bibliographies of retrieved articles were searched for additional references. Eleven reports were located that met the four inclusion criteria: original study, published in English or French, controlled trial (nonrandomized or randomized) of a geriatric medical service, and inclusion of at least one measure of mental state in the study. Ten reports met the validity criteria for intervention studies. There was little evidence that geriatric medical services improved the mental state of aged patients; all trials had limitations in design and measures. These findings challenge mental health professionals in two ways: first, services must be developed to address the apparently unmet mental health needs of aged medical patients; second, research methods must be developed to measure the impact of these services.