The mature endosperm of Croton bonplandianum proliferated profusely on White's medium (WM) + 2 ppm 2,4-D + 5 ppm kinetin + 2500 ppm yeast extract. Association with the embryo was essential for initiation of proliferation of mature endosperm. Tracheidal cells usually differentiated. Twelve-month-old callus contained predominantly triploid and hexaploid cells. When the callus obtained on WM + 2,4-D + kinetin + yeast extract was subcultured on WM triploid roots formed in 25% of the cultures. At 10−7 M, IBA, IAA, or NAA, in WM, promoted rooting; IBA was most effective. Attempts to induce shoot differentiation failed.