The effect of heat-shock on cell growth and the induction of recombinant protein synthesis by a temperature-sensitive (ts) Chinese hamster ovary (CHO) cell line was investigated. An optimal regime of successive 2 hour heat-shocks (42 degrees C) over 72 hours was found to simultaneously arrest cell growth and induce the synthesis of recombinant protein. The enhanced induction achieved from growth arrested cells may find application in the production of cytotoxic proteins.