A genetic case-control study was conducted in a group of patients with schizophrenia (n = 67; DSM-III) and psychiatrically normal controls matched for ethnicity (n = 84), living in the same geographical area. Using three different DNA polymorphisms of the gene encoding porphobilinogen deaminase (PBGD), a candidate gene for schizophrenia, an association with schizophrenia could not be detected. No significant associations were detected even after sub-division of the cohort by ethnicity and by gender.