Numerous factors have been advanced to explain electoral turnout. This paper puts the emphasis on two main categories of determinants: socio-economic and political. Numerous studies have shown that turnout increases with the socio-economic status of the voters. In the Johannesburg case, this study shows that, contrary to the usual finding, turnout is higher in the most deprived wards. Among the political factors, this paper studies the influence of the closeness of the electoral race on turnout. And there again the result is different from the usual one. In Johannesburg, turnout decreases with the degree of electoral closeness. Different specificities of the South African political situation may help to understand these unexpected results.