This paper uses a simple economic model of contract choice to explain the growth of sharecropping in sixteenth- and seventeenth- century France - a topic that figures in much of the social and economic history of the period. The theory turns out to fit both qualitative and quantitative evidence, and although the results are as yet only preliminary, the theory does provide a better account of the spread of sharecropping than the explanations early modern historians have tended to rely upon.