A circadian leaf movement has been found in Phaseolus vulgaris var. Pinto that will persist under constant temperature and continuous fluorescent light. The period of leaf movement was approximately 26 hours in length, and the amplitude did not diminish for at least 4 weeks. Leaf movements were similar for plants grown in either 1100, 4950, 7700, or 10,450 lumens per square meter. This is the first clearly defined persistent circadian rhythm reported for leaves of higher plants.