The analysis of labour supply under uncertainty has been developing rapidly in recent years. Papers by Block and Heineke (1973), Stiglitz (1976), Cowell (1981a, b), Eaton and Rosen (1980a, b), Stern (1980) and Tressler and Menezes (1980) have all presented analyses of the problem. Almost without exception, the focus of the analysis has been the effects of (in the rate or in non-labour income) on the labour supply decision of the individual. Not surprisingly, therefore, the well-known comparative static results of Rothschild and Stiglitz (1971) and Diamond and Stiglitz (1974), on how increases in risk influence the optimal choice of a control variable, have been found to be useful in this literature. Some of the above-mentioned papers have also considered the problem of labour supply under uncertainty when there are taxes in operation. Thus Stiglitz (1976), Cowell (1981a, b) and Eaton and Rosen (1980a, b) all analyse the role of taxation. However, none of these papers has examined labour supply under uncertainty with regimes of the type we observe in practicewhich are typically piecewise-linear.1 Moreover, in all the studies I am aware of the regime itself is held to be constant-thus, the role of tax risk, as opposed to wage risk, remains unanalysed. The object of this paper, therefore, is to advance the literature on labour supply under uncertainty in these two directions. First, we ask the more common question about the impact of greater risk on labour supply, but this time in the context of piecewise-linear regimes. It will be seen that the answers now have to be modified in interesting ways. In particular, it will be shown that the problem belongs to a general class of problems in decision-making under uncertainty, analysed in Kanbur (1980, 1982), where the pay-off function has a kink (or non-differentiability) at a critical value of the random variable. In such a setting the Rothschild-Stiglitz (1971) and Diamond-Stiglitz (1974) results are no longer directly applicable. We have to use their generalized counterparts, developed in Kanbur (1981). Second, we ask a question that has not been asked in the literature up to now: what is the impact of greater uncertainty about the regime on labour supply decisions? It will be seen that the piecewise-linear regime allows us to parametrize such regime risk in a convenient and manageable way. The plan of this paper is as follows. Section I introduces the model and, in the context of the model, gives a precise statement of the questions that this paper asks. Section II begins the analysis by considering the effects of greater risk in the rate and in non-labour income. Sections III and IV then consider the question of regime risk. Section V concludes the paper.