Consideration of a mechanism of action of colchicine in gout mediated by polymorphonuclear leukocytes ( PMNL ) should include interference with the system which directs PMNL to foci of acute inflammation. Based en the presumption of a chemical mediator, the directed migration of PMNL has been referred to as chemotaxis. Camera lucida studies have shown that a variety of bacteria are chemotactic, that is attract PMNL by converting their random wanderings into directed locomotion toward the bacteria.l Subsequently Boyden has described a simple technic in which filters with pores so small that PMNL can cross to the other side only by active migration, were used to study the chemotactic migration of PMNL toward substances placed on the other side of the filters2 Utilizing this technic, the effect of colchicine on the migration of human PMNL through millipore filters with pores 3.0 microns in diameter toward suspensions of S.albus on the other side was investigated in a series of ex- periments3 In each experiment, leukocytes from the blood of a healthy human volunteer were placed in the compartment above the filter in multiple chambers, containing in the compartment below the filter either plain nutrient so- lution (control chambers) or a suspension of S.albus (bacteria chambers). To some of the bacteria chambers colchicine was added, providing the same concentration in both the compartments (bacteria colchicine chambers). Each combination of contents was set up in duplicate. The chambers were then incubated at 37Β°C for three hours, after which the filters were removed, fixed,