This study was carried out to investigate the effect of paclobutrazol, a gibberellin synthesis inhibitor in young rubber plants and standardise its optimum concentration to develop better root system. Paclobutrazol treatment in young rubber (Hevea brasiliensis) plants resulted in short and compact plants having dark green leaves, with more fibrous root development and improved root-to-shoot ratio. Plants of Hevea clone RRII 429 were treated with 0, 50, 100, 250, 500 and 750mg active ingredient of paclobutrazol per plant as soil application. Three months after treatment the leaves showed increased chlorophyll (25.9;) and carotenoid (33.6;) contents over control. The height increment in paclobutrazol (50 mg) treated plants was significantly lower than control plants of same age, whereas, the girth increment was significantly higher (10.9;) in the treated plants. Paclobutrazol treatment remarkably increased root dry weight (maximum of 132 per cent with 50 mg) and root-to-shoot ratio. The results indicated that paclobutrazol at a concentration of 50 mg was optimum for more fibrous root development without any significant changes in stem girth and leaf number. The modified root system may likely be an advantage to young Hevea plants during drought.