In a test of replacement of queens in queenright colonies, mature queen cells (within about a day of queen emergence) were introduced into honey supers during the nectar flow. In the period 1977-1979 a queen cell was introduced into each of 919 colonies. An examination made 5 days after cell introduction showed that queens had successfully emerged from 70'3% of the cells, while 11'1% of the cells had been destroyed, 5'7% contained dead queens, and 12'9% were not found. In a comparison of overwintered and package colonies in 1978, in overwintered colonies significantly more queens emerged (61% vs 44%) and significantly fewer cells were destroyed (8'9% vs 25%). Of 474 introductions in 1978-1979 only 12'7% resulted in successful requeening, whereas 53% of the resident queens were retained and 24% were replaced by new queens reared in the colonies.