SummaryBrood survival in 51 bee colonies was investigated. Of those, 15 were in an apiary where bee breeding was not practised and the queens mated at the apiary; 20 had queens mated in the mating stations of 4 professional queen breeders; 16 had queens that were each instrumentally inseminated with semen from 1 drone only. About 7% of larvae disappeared from the combs during the first developmental stages through factors other than ones related to sex alleles. The overall survival rate in colonies with queens mated naturally was about 85%, whether the queens were mated in the apiary or in mating stations. Thus the brood survival permitted by the sex alleles was 92%, which indicates the presence of about 12 sex alleles in the populations. Thus a bee breeding system that expects the sex alleles to allow 85% brood survival is acceptable, although in practice, it may not appear to be so because the overall survival is only 78%.