Controversy continues regarding the differential diagnostic distinction between schizoaffective disorder and schizophrenia, and there are few published studies that examine the neuropsychological performance of schizoaffective patients. We evaluated 52 RDC-diagnosed schizophrenic and schizoaffective patients with equal numbers of medicated and unmedicated patients using the Luria-Nebraska Neuropsychological Battery and additional cognitive measures. Both groups performed at cognitively impaired levels. The cognitive performance level of schizoaffective patients was indistinguishable from that of the schizophrenic patients. The RDC subtype of schizoaffective disorder (depressed or manic) also was not related to cognitive performance level. Findings are consistent with the notion that cognitive impairment is found in a significant portion of schizophrenic (and possibly schizoaffective) patients and that the presence of this deficit may characterize a specific subgroup of patients.