Thesis (MDip (Medical Technology))--Cape Technikon, 1993 / The use of genetic marker testing to resolve cases of disputed paternity, is well established. The number and range of systems used depends on the expertise of the laboratory, and for this reason various laboratories offer different systems. Standard testing includes tests in the following genetic marker systems: human leukocyte antigen (tissue) typing; red cell blood groups; and red cell enzyme and serum protein testing. The Provincial Laboratory for Tissue Immunology currently offers a range of 16 genetic marker systems capable of excluding >99% of falsely accused men. Following the discovery DNA polymorphisms, particularly VNTR DNA polymorphisms, and the commercial availability of VNTR DNA probes, PLTI decided to offer this service to our clients. This study was the initial phase in the establishment of a VNTR DNA typing laboratory and covered the determination of inter-and intra-gel accuracy and precision, selection of restriction enzyme/probe combination, and evaluation and comparison of the results of 100 disputed paternity cases tested using both standard and VNTR DNA typing. Of the 100 cases tested, in 33 cases, the putative father was excluded using standard testing. These exclusions were confirmed using VNTR DNA typing, and, furthermore, an additional two exclusions of paternity were shown using only VNTR DNA typing. In another two cases of disputed paternity, the exclusions obtained using standard tests required further confirmation. VNTR DNA typing convincingly excluded both falsely accused putative fathers. The VNTR DNA typing laboratory now functions as an integral part of the disputed paternity service. Due to the cost and time involved in VNTR DNA typing it is reserved at this stage for: those cases which require further confirmation of the results of standard testing; when the probability of paternity is low (<99.7%); or when a specific request is made.