The effect of different diapause regimes on diapause survival and post-diapause performance of queens of the bumble bee Bombus terrestris was determined in an attempt to establish optimal diapause condition for mass rearing. Mated queens were randomly divided into four groups and subjected to one of four diapause regimes: anesthetized with CO2 (non hibernated); or hibernated for 45, 75 or 105 days at 4.5 +/- 0.5 degrees C and anesthetized with CO2. Queens hibernated for 45 days had the highest survival (80.68%). Survival decreased with increasing duration of diapause. Although non hibernated queens produced significantly more workers, males and queens than the hibernated queens, egg laying rate and colony production (more than 10 workers emerged) rate were much lower in the non hibernated queens than in the hibernated queens. The highest egg laying and colony production rates were found in the 45 days hibernated treatment (90% and 80% respectively). In terms of the lowest diapause mortality and highest post-diapause performance, therefore, hibernating queens for 45 days at 4.5 +/- 0.5 degrees C and then anesthetizing them with CO2 appears to be the best diapause regime for mass rearing of B. terrestris.