SummaryA new pedigree of post‐axial Polydactyly concerned with four generations in a family of the Batutsi tribe is presented. Only one of the family members examined was affected; his hands showed typical extra‐digit‐V hexadactyly but his feet had different abnormalities. No documentary evidence existed and the pedigree was constructed from verbal information. Irregular dominance of the trait is shown, and it is deduced that the mode of inheritance can be explained by postulating two dominant genes, one of which controls the penetrance of the Polydactyly gene.Mr R. G. Passmore brought Bakundukize to the writer's notice and Mr H. L. Manning and Drs A. G. M. Davies and J. E. Dale criticized the manuscript. Mr T. Eddie kindly provided the X‐ray ne