The effect of coconut water (CW) and of 2,4-dichlorophenoxyacetic acid (2,4-D), applied singly or in combination, to clonal material of excised roots of tomato cv. ‘Moneydor’ was investigated. Distinct stimulatory effects on the growth of roots were obtained in both cases. CW showed its highest growth action when applied at low concentrations (0.025% and 0.050% v/v) to roots incubated in darkness. Certain combinations of CW and 2,4-D gave a strikingly high growth rate which exceeded that of the control with or without CW. A combination of 2 x 10-4 p.g. ml of 2,4-D with 0.050% (v/v) of CW gave maximum growth stimulation without toxicity to the root tissue.