Abstract Multiplication of Clostridium botulinum in honey-bees was examined to explain the heavy contamination of honey which may occur with this pathogen. When dead bees were inoculated with C. botulinum spores at levels of 10 2−10 3 and incubated aerobically for 10 days, the organisms increased to 10 4−10 5. When botulinum spores were inoculated together with Bacillus alvei, the growth of most strains was significantly enhanced (10 5−10 7). Similar results were obtained in bee pupae, but not in bee larvae. The heavy contamination of honey with botulinum spores that we have sometimes encountered may have been caused by contamination from dead bees in which C. botulinum had proliferated.