The article aims at understanding the determinants of ministerial turnover in presidential systems. There are essentially three key factors that govern the propensity for ministerial turnover in a presidential system: 01. political ambition - reflected in the individual or collective strategies and tactics employed by the party-affiliated actors represented in the cabinet; 02. the presence or absence of a governing coalition - which has bearing on the degree of ideological distance between the president and such political parties as form part of any governing coalition, with consequences for ministerial scrutiny; and 03. accountability - a determinant in responding to such external pressures as may be brought to bear by public opinion. In order to investigate the impacts of these factors, this inquiry seeks to analyze the new and dynamic democracy of Brazil. Brazil's presidential system presents interesting features that make it an excellent laboratory in which to test hypotheses concerning every aspect of ministerial turnover. To this end, this paper employs a multivariate methodology, as well as descriptive and survival analyses, based on a comprehensive and original database of cabinet ministers that draws on three presidencies over five democratically elected governments from 1995 to 2014. Among other results, our most original finding was that there is an inverse correlation between the degree of ministerial politicization (political ambition) and ideological distance from the president during political scandals (interaction between the governing coalition and accountability) on the one hand, and the length of ministerial tenure on the other.