Haptoglobin subtyping of a Danish population sample (n = 2184) by a modified isoelectric focusing/immunoblotting method, using agarose gel and visualization by an alkaline phosphatase conjugated antibody, is presented. The allele frequencies were: Hp*1F 0.151; Hp*1S 0.241; Hp*2FS 0.565; Hp*2SS 0.040; Hp*2FF 0.002; Hp J*0.0002. Based on these data the theoretical change of exclusion of nonfathers in paternity cases was calculated to be 35%. Examination of 51 families with 120 children and of 648 mother/child pairs showed no exceptions from Mendelian inheritance. The results obtained by application of Hp subtyping to 405 paternity cases are given and the reliability of the method is discussed. A new alpha 2-variant occurring in the father and in two of three siblings of a Danish family is presented.