This study evaluated the impacts of bST on the profitability of representative Pennsylvania dairy farms using a stochastic simulation model under two initial milk yield-per-cow levels, three levels of milk response to bST, and three milk price forecast scenarios. Results showed that farm profitability was improved with bST, but the magnitude of the benefits from bST depended on the farm's initial milk output per cow and the level of milk response to bST, both of which are related to quality of management. However, modest price declines due to bST-induced increases in the milk supply would have an offsetting effect on farm profitability.