In the studies of performance tests of surface active agents, a new semimicro continuous method of wetting test, the “Tensiometer Method” has been developed in our laboratory. The method consists of measuring the change of apparent density of a standard canvas or felt disc, immersed in a test solution, with Du Nouy tensiometer. The change of apparent density is plotted against time on semi-log paper, and the entire progress of wetting is clearly shown by the apparent density-time curves. The method is simple, accurate, needs only very small quantities of test solutions, can be applide to dye-, mercerisation- and other transparent and opaque processing solutions, and also serves as rewetting test.