Leptospirosis is a disease of global importance with a changing epidemiology in both humans and animals. It is also a significant zoonosis particularly in the developing world. To date there is limited knowledge of the incidence of leptospirosis in dogs in South Africa. This study was undertaken on a subset of dogs in South Africa to determine the presence of leptospiral antibodies to serovars known to infect dogs. Serum samples from both stray and owned dogs from various parts of South Africa were collected and tested against fifteen serovars of Leptospira. Five hundred and thirty samples were tested and twenty-five tested positive to seven different serovars. Nine of the 25 samples tested positive to more than one serovar. The two serovars that were most frequently represented were L. Canicola, which reacted to seventeen sera, and L. Pyrogenes, which reacted to nine sera in all. Currently the only vaccines available in South Africa in different combinations contain either L. Canicola, L. Icterohaemorrhagiae, L. Pomona or L. Grippotyphosa. The results show that the use of vaccines containing L. Canicola is still justifiable in certain regions of the country. However, the presence of antibodies to L. Pyrogenes in several dogs indicates that there is a need to investigate for the presence of antibodies in a larger group of dogs. This would allow vaccine manufacturers to tailor the Leptospira antigens present in vaccines to include those that are prevalent in a particular region or country. Copyright / Dissertation (MSc)--University of Pretoria, 2009. / Veterinary Tropical Diseases / unrestricted