First admissions for schizophrenia in Northern Ireland are significantly higher for the Roman Catholics than for the rest of the population, although not as high as in the Irish Republic. The excess of Catholic cases affects only the never-married, and derives much more from the rural west of the territory than from the industrial east. It does not appear to be accounted for by geography per se, by the differential use of services, diagnostic bias, social class distribution, or mean age at marriage. There are indications that some conflict around sex and marriage and, more doubtfully, a sense of relative deprivation may be contributing factors.