The effect of 3,6-dichloro-o-anisic acid (dicamba) on common purslane (Portulaca oleracea L.) was studied under growth room conditions. Common purslane was quite sensitive to dicamba. The lethal rate depended on the age of the plants and increased with their development. The visual responses included bending of young stems, epinasty of leaves, and inhibition of nyctinasty, followed by necrosis of leaves, defoliation, swelling of stems, and death of the growing tips with loss of apical dominance. Stem elongation was inhibited and fresh weight of tops was markedly reduced by dicamba application to either the roots or foliage. Carboxyl-labeled dicamba-7-14C was absorbed slowly by common purslane leaves. However, translocation appeared rapid, with accumulation of dicamba observed in the young tissues. A small amount of dicamba was exuded through the roots. There was no indication of dicamba degradation in common purslane during 8 days following treatment.