An experiment, envolving diploid and polyploid clones of Hevea brasiliensis was mounted In the field with the objective οf a comparative. study of hydric ballance. The fallowing parameters were analyzed: faliar, hydric potential, stomatal resistence, transpiration, percent of water content, foliar saturation deficit, micro-estructure of epidermis, and the índice of hydric efficiency. In general the. results suggest that the polyploid clone IAC-222 has the greatest hydric capacity, and consequently its large lndince of hydric efficiency can be defined as an advantage over the diploid in terms of water retention during critical, periods.