In order to explore whether suicides had a distribution of blood groups that differed from the general population, samples of 560 completed suicides & 166 attempted suicides in Budapest in 1991 were blood typed. Completed suicides were more often Type O than attempted suicides, & they tended to be more often Type O than the general population. This result was interpreted in the light of research showing that samples of bipolar affective disorder patients may have an excess of Type O individuals. (11 refs.)