Abstract A sterile culture technique for studying the formation and differentiation of cambial derivatives in isolated stem segments has been successfully developed. One- or two-year-old stem segments (50-70 mm long) are surface-sterilized and their ends aseptically fitted into sterile latex tubing attached to a glass reservoir containing the liquid medium. The stems are fed fresh medium daily by opening and closing clamps above and below the points of their insertion. Stems of Pinus densiflora Sieb. and Zucc. and Larix leptolepis Endl. were grown on a defined medium for 28 days during which time several new xylem elements were formed which differentiated into normal lignified tracheids of the earlywood type. The technique will be useful in studying factors affecting cambial activity and the differentiation of cambial derivatives under controlled nutritional and environmental conditions.