A major role of the serotonergic system has been hypothesized in the pathogenesis of schizophrenia, mostly based on the evidence of action of new and atypical neuroleptics such as Risperidone or Clozapine. We evaluated the genotypes and alleles of the 5HT2a receptor gene in 67 nuclear families following the Haplotype Relative Risk (HRR) strategy and in a second sample of 100 schizophrenics and 103 controls. The 5HT2a receptor gene polymorphism, following PCR amplification and subsequent Hpa II digestion, reveals a two-alleles system in the coding region of the gene. We did not find statistically significant differences between patients and controls for genotypes, nor for alleles, both in the HRR and in the case-control groups. These results do not confirm the positive association obtained by Inayama et al.: [Neuropsychopharmacology 1(35): 145-219, 1994] and by Williams et al. [Lancet, 397:1294-1296, 1996] in our population.