A b st r a c tThe remaining cholineaterase activity after incubation with paraoxon (as an indicator of the activity of human serumparaoxoneee) shows a distribution with three cluatem which could be explained, after an investigation of familie.6, by a simple two-allele-model. A Btochastical outaide criterion is given by the constellationa of the V8lUeE within the families.By modification of an iteration method deacribed by FANGMEYEB (1964) it is possible to estimate the distributions and frequencies of the three groups. A simulation study shows that the combination of the used method with the pure cluster analysis advantageous.Key wordr, : Stochaetical &ide criterion, mixed dhlribution, c l~t e r analysis; twoallele-model, enzyme plynwrphiem, serumparaoxona8e, analysis of multipeak dislributione.