Polymorphic variants of C3, BF and C6 complement factors have been investigated in schizophrenic patients subdivided according to the existence or not of a family history of both schizophrenia and other psychiatric disorders. To analyze the contingency tables, besides the usual methods, log-linear models have been fitted. Significant associations have been found in the C3 system, with a decrease of C3*F in patients (contradicting previous findings), and in the BF system, with a decrease of FS phenotype among patients (confirming some previous results). No association has been found for the C6 polymorphism (in accordance to previous results). Therefore, the present findings only partially confirm previous results and do not clarify the relationship between complement genetic markers and schizophrenia, stressing some statistical difficulties.