Several linkage analyses in schizophrenia research point to a locus on chromosome 6p22, where the gene coding for tumor necrosis factor-alpha (TNF-alpha) is located. A marked influence of antipsychotic medication on TNF-alpha has been described. As the involvement of an immune process in the pathophysiology of schizophrenia has been discussed, a functional TNF-alpha polymorphism appears to be a candidate in genetic schizophrenia research. The G308A polymorphism of the TNF-alpha gene was described to be associated with increased TNF-alpha production. Boin and colleagues have already described a significant association between the polymorphic allele and schizophrenia, investigating 84 schizophrenic patients (21 % polymorphic allele) and 138 healthy volunteers (11 % polymorphic allele), recruited in Northern Italy. We carried out a replication study including 157 schizophrenic patients and 186 healthy persons, who were recruited in Southern Germany. Psychopathology was additionally monitored by PANSS. We were not able to replicate the findings of Boin et al., as we did not find any difference in allele frequency or genotype distribution between our schizophrenic patients (13.7 % polymorphic allele) and healthy controls (16.9 % polymorphic allele). Moreover, we did not find any association between genotype and psychopathology, as measured by PANSS. The different results between these two studies may be due to ethnic differences.