In a randomized field experiment, we investigate the interplay between work goals, monetary incentives, and work performance. Employees are observed in a natural work environment where they have to do a simple, effort-intense task. Output is perfectly observable and workers are paid for performance. While a regular piece-rate contract serves as a benchmark, in some treatments workers are paid a bonus conditional on reaching a pre-specified goal. We observe that the use of personal work goals leads to a significant output increase. This is found if goals are self-chosen by the workers, as well as if goals are set exogenously by the principal -although in the latter case, the exact size of the goal plays a crucial role. Strikingly, the positive effect of self-chosen goals persists even if the goal is not backed up by monetary incentives. Our results suggest that work contracts where -through the choice of a personal work goal -workers themselves determine the risk and the size of their bonus payment at the same time can be a powerful incentive device.JEL classification: A12, C93, D01, D03, D24, J24, J33, M52