Requests for blood tests to resolve issues of disputed paternity fall under three main categories: (1) Proof of adultery; (2) Proof of kinship (a) in claims for citizenship, (b) to make material changes to the Birth Certificate, (c) for settlement of family disputes usually in inheritance matters; and (3) Investigation of sex crimes like rape and incest where a child is the result of the union. A broad overview is given on the venous red cell and serum blood groups used for paternity investigations. The laws of inheritance as applied to blood group investigations for disputed paternity are discussed. A survey of cases investigated on red cell and serum genetic markers since 1978 till 1990 showed an average of 5.5 cases a year with exclusion of the putative father in 19% of cases.