Abstract
Properdin factor B (Bf) was phenotyped on 519 paternity cases. Gene frequencies of BfF= 0.1870, 5fF1 = 0.0105, Bfs= 0.7985 and Bfs0.7= 0.0040 were observed in Minnesota Whites. Based on these values the exclusion probability is (p) = 0.1442. Bf accounted for 15% of the 88 observed exclusions. A technique is described for simultaneous elelctrophoresis of Bf and Gc on the same gel.