During the 1990s, a large number of regulatory agencies were created or reformed in different sectors in Latin American countries. Almost all included political delegation mechanisms, intended as formal rules to enhance credible commitments to time-consistent policies. In this paper, using an original data set of agencies’ head tenure in the telecommunications and finance regulatory agencies, we discuss if these mechanisms worked as planned, and find a divergence between actual mandates and the formally established fixed terms, effected by means of systematic early resignations. Our findings reveal, however, some consistent patterns of behavior. Stronger legislative presidential power reduced effective delegation to some extent, and agencies’ organizational strengths protected them from patron-age. We also confirmed the existence of some significant differences be-tween the two sectors examined. Having slightly weaker delegation rules, delegation practices were also less effective in telecommunications than in financial services, contrary to expectations about credible commitments.