Employment contracts generally specify both the reward for labour and the conditions of employment. Although it is clear how unions affect the payment received by workers, the effect of unions upon working conditions, particularly the contracted effort level that must be supplied, is not so well-understood. This note analyses the generalised Nash bargain between a union and a firm over employment level and effort level. Under standard assumptions, it is shown that an increase in union power always leads to a reduction in the agreed effort level. The effect upon employment is dependent upon whether the firm has the right-to-manage .