Root architecture is closely related to P acquisition efficiency. In the present study, effects of P availability on the root architectural responses of different common bean genotypes were examined. Four common bean (Phaseolus vulgaris L.) genotypes representing different origins and ecotypic races were compared in a strat ified mesh soil potculture system and root architectural parameters were analyzed with computer image analysis. The results showed that root biomass, total root length and total root surface area were decreased under low P conditions. The P efficient genotypes had a larger, finer and shallower root system than the P inefficient genotypes. The basal roots of G19833, G19839 became shallower while those of DOR364 became deeper under low P conditions. The results from this study suggest that there is great genetic variation in root architectural responses to P availability. The genetic potential of root architectural response provides possibility of selecting this trait for improving P acquisition efficiency in common bean.