A series of experiments have been conducted using a recombinant baculovirus/insect cell expression system (Bm5/BmS.NPV.CAT) to establish the optimum temperature for both cell growth and virus infection. Bm5 cell growth was found to be limited at temperatures below 22 degrees C and ceased completely at temperatures above 34 degrees C. In the range between 24 and 28 degrees C, final cell densities always reached 96% of the highest achievable viable cell density. The shortest population doubling time was obtained at 28 degrees C. Overall, a consistent increase in metabolism with increasing temperatures was observed. During the infection/viral replication phase, an increase in the temperature from 25 to 31 degrees C resulted in a faster decrease in viable cell density and an earlier production of chloramphenicol acetyltransferase (CAT). Furthermore, protein yield at temperatures above 28 degrees C was significantly reduced. Overall, the best temperature for the infection phase for the Bm5/Bm5.NPV expression system was found to be 25 degrees C when the cells are cultured in serum free media.