The effect of slip on detwinning behavior of a wrought Mg alloy has been investigated, using a micro-grid method to measure the local strain. Two compression paths were designed. In one case compression was applied first along a direction promoting twinning, and then along a perpendicular direction promoting detwinning. In the second an intermediate deformation along a direction midway between these two directions was applied to promote basal slip. It is shown that a smaller strain is required for detwinning than for the initial twinning. Moreover, the interaction between basal 〈a〉 slip and twinning accelerates the detwinning behavior.