In this paper, a risk-based unit commitment (RBUC) approach for the day-ahead market is introduced. A risk-based economic dispatch, an independent part of the risk- based unit commitment, can be used for the real-time market. This provides for consideration of both economic benefit as well as reliability within a single integrated approach. A three-stage stochastic programming problem is formulated and solved using Benders decomposition to give a balance between the economic benefit and the risk. The approach is illustrated on a six-bus test system.