Polymorphonuclear leucocyte (PMN) function was studied in 7 healthy subjects before and after 5 mg of colchicine taken in divided doses over 24 hours. Mean adherence to nylon fibre columns fell from a pretreatment level of 51% to 33.6% by day 1, remained low (31.8%) at day 5, and returned to pretreatment levels only by about day 9. Random motility (agarose plate method) fell from 932 μm to 688 μm by day 1, but had returned to normal by day 5. Directed migration and the phagocytic index (opsonised Candida albicans method) were not affected by colchicine treatment. In view of the fact that the plasma half life of colchicine is 19 minutes and that of PMN only 7 hours, this marked and prolonged reduction in PMN adhesion implies an influence on maturing PMN precursors in bone marrow. Adherence to nylon fibres may reflect in-vivo properties of PMN which are important in the pathogenesis of acute gouty arthritis.