In a sample of 1.033 diabetic patients characteristics of 10 group specific systems (ABO, MNS, Rh, P, K and Fy blood groups and Hp, Gc and Gm serum types) were tested in order to verify any association of hereditary group specific traits and diabetes. The patients were subgrouped for sex, seriousness of diabetes, age of manifestation and body type. The frequencies of the group specific traits were statistically compared with those of an appropriate control group using the chi2 test. Resulting from that investigation an increase of blood group 0 was found in diabetes below average in corpulence (basing upon the Rohrer index), and a confirmation was found for an already suspected association of diabetes and the Gm (a plus x plus) type.