Development in solving parentage problems has not progressed at the same pace in all countries and has been influenced by prevailing legal systems and social climate. The United States has, on the whole, remained conservative about the application of many of the newly developed systems to paternity tests. Northern European countries, Germany, and Holland have forged rapidly ahead. Great Britain remains in a position midway between the United States and the previously mentioned European countries. In England, blood tests are made at the direction of the court when paternity is at issue. Tests are made for red cell antigens, serum types, and red cell enzyme polymorphisms. A comprehensive list of systems typically investigated by British specialists dealing with paternity problems provides an overall chance of excluding wrongly named putative fathers 93 percent of the time; a list provided by a German specialist shows a combined exclusion chance of 99.948 percent. The determination that one man is the father of a particular child is impossible, but exclusion of wrongly identified fathers could increase through expansion of polymorphisms and continued expansion of newly discovered systems. The improved techniques for exclusion will aid in processing civil actions for child support and divorce, and in prosecuting criminal charges of incest, rape, and kidnapping. Tables and footnotes are included.