1. 942 resp. 821 patients with psychic disorders (843 resp. 339 patients with neurotic disorders, 443 resp. 191 patients with manic-depressive psychoses, 436 resp. 193 patients with schizophrenic psychoses, 220 resp. 98 patients with organic syndromes) are compared with regard to the distribution of the ABO blood groups and the Rh-Factor with 5.000 normal controls and of the MNS blood group with the expected distribution respectively. Significant differences are demonstrated: AB (-2.63%, P less than 0.10) in organic syndromes; Rh+ (+3.65%, P less than 0.02) in neurotic disorders; Rh+ (+3.10%, P less than 0.005) in all diagnoses; 0, Rh+ (+4.31%, P less than 0,05) in neurotic disorders; AB, Rh+ (+2.29%, P less than 0.05) in manic-depressive psychoses; A, Rh- (-1.59%, P less than 0.05) in all diagnoses; AB, Rh- (-0.58%, P less than 0.05) in all diagnoses; MNS (Ms +2.26%, MS +2.10%, MNs -3.65%, MNS -0.35%, Ns +0.52%, NS -0.88%, P less than 0.05) in all diagnoses. The results are compared with the literature, and methodical problems are discussed.