The migrations of infective larvae of sheep and horse Strongyles have been studied by various workers, principally in relation to their behaviour in faeces or in different types of soil. (Bruns, 1937 and Lucker, 1938). The factors affecting the extent and nature of the migrations of certain infective larvae on to grass have also received attention (Rogers, 1940). A knowledge of the behaviour of larvae both in soil and on grass is very necessary if control methods either by chemicals or by controlled pasturing are to be effective. The present paper, however, describes an attempt to study the fundamental behaviour of these larvae in the laboratory, in the hope of obtaining results of practical value or of filling up certain gaps in our knowledge of them. A simple technique was sought, whereby the migrations of the larvae could be studied in the laboratory under different conditions, and is described herein.