A recent study identified a putative association between variants in the regulator of G-protein signalling 4 (RGS4) and schizophrenia, Chowdari et al. [2002: Hum Mol Genet 11: 1373-1380]. RGS4 is both a positional and functional candidate gene for schizophrenia. Chowdari and colleagues identified association at this locus in a number of distinct and ethnically diverse samples, although the pattern of association was not the same in all the samples. Our study attempted to replicate this association in an independent Irish sample of schizophrenia cases and controls. We succeeded in detecting evidence of association at the RGS4 locus. The signal comes from a four-marker haplotype that is in significant excess in our case sample. The same haplotype is in excess in the Caucasian schizophrenia sample used by Chowdari et al. [2002: Hum Mol Genet 11: 1373-1380]. This study provides further support for the contribution of RGS4 to schizophrenia susceptibility.