Swarming is an important process in honey bee (Apis mellifera L) colonies, yet very little is known about the physiological changes in workers that are preparing to swarm. In this study we determined the physiological status of worker honey bees in pre-swarming colonies and in normal (non-swarming) colonies. Juvenile hormone (JH) titers in worker bees were similar in both groups before queen cells were present, but became significantly lower in pre-swarming colonies compared to normal colonies when queen cells appeared in pre-swarming colonies. The lower JH titers in the pre-swarming colonies suggest that behavior development is delayed in these colonies, consistent with previous reports that pre-swarming colonies have reduced foraging activities. Hemolymph Na+/ K+ ratio became significantly higher in the pre-swarming colonies in two out of three trials. This is also consistent with our hypothesis that the Na+/ K+ ratio should be higher in bees preparing to swarm. Determining the physiological correlates of bees preparing for swarming will help us better understand the biology of swarming.