What explains bloc voting among ethnic groups in Africa? Using the Her?ndahl Hirschman Index of Concentration on partisan preference data from the Afrobarometer, this article tests several hypotheses regarding the explanation as to why some ethnic groups: (1) express voting preferences as a bloc; (2) express voting preferences as a bloc for the governing party or the opposition. This article found that the geographic concentration of the group best explained general bloc voting. In terms of the direction of support, the degree to which a group is discriminated against and politically mobilized explains bloc voting against the governing party, whereas bloc voting for the governing party is explained by the extent to which the governing party is politically dominant. This suggests that the prospects for patronage helps explain voting as a bloc for most all groups, except those that face discrimination and are politically mobilized.