The P/Q type Ca2+ channel alpha 1-subunit (CACN1A4) gene on chromosome 19p13 is a promising candidate susceptibility locus for schizophrenia. Point mutations in CACN1A4 cause familial hemiplegic migraine and episodic ataxia. Expansion in a coding 3' CAG repeat causes spino-cerebellar ataxia type 6 (SCA6). The mouse mutant phenotype totterer has a form of petit-mal epilepsy. These are neurological conditions, all of which exhibit features in common with schizophrenia. The 19p13 area is also paralogous to other genomic regions of interest in schizophrenia genetics. For these reasons, we performed an association study with the CAG repeat and schizophrenia using 225 Scottish schizophrenia and 198 unrelated Scottish controls. The repeat was not associated with the disorder (P = 0.72) and neither did the schizophrenics have significantly longer alleles than the controls (P = 0.45). We conclude that the SCA6 CAG repeat is not associated with schizophrenia susceptibility. However, it remains possible that other variants in the region could be involved.