SummaryWorker honeybees in cages, fed on honey and pollen treated with ethylene oxide at 900 g/m3without subsequent ventilation, did not show a higher mortality than controls. Mice fed on honey similarly treated showed neither pathological alterations in liver and kidneys, nor higher mortality, than controls. On the other hand, the addition of ethylene glycol to honey, at a concentration as low as 1·25% by weight, had a toxic action in bees, and in mice a concentration of 0·78% caused toxic damage to the liver (steatosis). The effectiveness of the ethylene oxide treatment on vegetative forms and spores ofBacillus larvae(except in dry scales), and on other micro-organisms, was confirmed.