In a persuasion problem, an informed agent uses limited evidence disclosure to communicate with the principal who chooses an outcome. We focus on the eff ect of introducing cheap talk and we show how it can be benefi cial to the principal. We study determinism and credibility under the assumption that the principal's utility function is a concave transformation of the agent's utility function. We show that randomization is unnecessary if the principal's action space is continuous, but is generally needed if it is discrete. In that case, there exists an optimal solution such that every randomization involves only two actions. However, commitment is necessary in both cases if unlimited evidence disclosure can improve the principal's payoff . In the absence of cheap talk and under the same assumption, neither randomization nor commitment over the outcome are necessary as shown in Sher [2011].