Ethnicity has emerged as a prominent issue in electoral contests around the world, particularly in countries that have embraced multiparty elections in the past few decades. What factors influence ethnic mobilization and the politicization of ethnicity? Although a number of factors have been hypothesized to influence the politicization of ethnicity in the comparative politics literature, many of these relationships have not been established through empirical testing. This study empirically tests a number of the hypotheses derived from the literature with our unique data set on candidates' ethnic appeals in the Nigerian 2007 gubernatorial elections. We find that political parties' use of ethnic appeals is correlated with the competitiveness of the election, nature of the campaign, partisan attachments, and social, demographic, and economic characteristics of the states. Of particular note is the finding that the salience of ethnic identity in the electorate influences political leaders' use of ethnic appeals.