This investigation reports an association study with alleles of the dopaminergic system genes (tyrosine hydroxylase (TH), D2 and D4 receptors) in schizophrenic patients and non-schizophrenic subjects. The genotypes were typed using a polymerase chain reactions PCR-based CA repeat polymorphisms. There were no significant associations between the studied alleles and schizophrenia. Also, a linkage analysis was performed using the same genes (TH, D2 and D4) in two multiple affected schizophrenic families. There was no linkage among any of three genes and schizophrenia. The maximum lod score (Z = 0.43, theta = 0.10 penetrance 100%) was for the tyrosine hydroxylase gene. Linkage analysis significantly excluded the D2 receptor gene (Z = 5.6, theta = 0.01), assuming an autosomal dominant pattern and complete penetrance, However, when the lod scores were calculated with other penetrance values, they lost significance.