Serological characteristics in 5 groups of patients and possible associations were investigated. In the group of patients with malignant melanoma, association was not found. Within patients in the group with chronic urinary infections, increased frequency of blood group B and non-secretor was found indicative, thus investigation will be continued. Association of blood group 0 and non-secretor was confirmed in the group of children with duodenal ulcers (this association was confirmed in adults and documented in literature). Association between Lewis system and schizophrenia has not been investigated until now. Relatively high frequency of Le (a b-) phenotype and relative risk of 4,0 were found in those patients.
