Several parts of the 12-d-old seedling of Phaseolus vulgaris L. cv. Red Kidney were surveyed for cellulase activity. The laminar abscission zone and the cotyledon were highest in total cellulase while the petiole, stem, leaf and root had lesser activity. A portion of the cellulase from each tissue was associated with a membrane fraction which equilibrated on a sucrose density gradient at a density of 1.16 g/cm(3). Fortification of the buffer with 1 M NaCl was necessary for complete extraction of cellulase from all tissues. Ethylene treatment enhanced cellulase activity in the laminar abscission zone, the petiolar pulvinus, and somewhat in the stem, but not in the petiole nor the nodal region of the stem. Thus, those tissues which are target tissues for ethylene action also showed ethylene-enhanced cellulase activity.