OBJECTIVE: The authors sought to estimate the prevalence of simple schizophrenia, compare the clinical presentations and courses of simple and "typical" schizophrenia, and examine psychopathology in first- degree relatives of probands with simple schizophrenia, probands with typical schizophrenia, and community comparison subjects. METHOD: The authors followed up all individuals with a recorded diagnosis of schizophrenia (N = 285) and 75% of those with a diagnosis of severe affective illness (N = 99) from the Roscommon County Case Register, which includes all individuals seeking psychiatric care in a rural county in western Ireland. The authors interviewed all available first- degree relatives of these groups and of matched unscreened community comparison subjects. RESULTS: Eleven cases of simple schizophrenia were diagnosed in the probands, for an estimated population prevalence and morbid risk in County Roscommon of 5.3 (SE = 1.6) and 6.2 (SE = 1.9) per 10,000, respectively. Individuals with typical schizophrenia (N = 126) had more marked delusions, hallucinations, and positive thought disorder; individuals with simple schizophrenia had more pronounced negative thought disorder and a more chronic course. Neither social/occupational functioning nor negative symptoms differed between the two groups. The risks for schizophrenia and all nonaffective psychoses were greater in the relatives of the probands with simple schizophrenia than in the relatives of the community comparison subjects. CONCLUSIONS: In this sample, simple schizophrenia was relatively rare, was rather debilitating, and resembled typical schizophrenia in presentation and course except for the absence of positive psychotic symptoms. From a familial perspective, simple schizophrenia appears to be related to typical schizophrenia.Abstract Teaser