Phosphorus deficiency is common in rice cultivated soils and particularly acting as a limiting factor in the acid sulfate and acid upland soils. Improved variety adapted to low soil-P condition is needed to reduce the need of P fertilizer and to increase rice yield. A study was conducted on the application of modified bulk selection method in rice breeding to develop lines adapted to low soil-P condition. The materials used in the study were two populations of F3 generation derived from crosses of IR6008023/Bernas Prima and Gampai/Progol. The materials were planted on P sub-optimum condition at Muara Experiment Station, Bogor, West Java, to obtain F4 and F5 population, selected using modified bulk method. The F5 population were planted on two environment conditions, namely on P optimum (36 kg/ha P2O5) and on P sub-optimum (without P fertilizer) to obtain F6 population. A total of 40 lines from each population were selected, so that 160 F6 lines were obtained. The F6 lines were evaluated on P+ and P- conditions, using augmented design. Result showed that selection for lines adapted to P- should be done on P- condition, whereas for those adapted to P+ could be done on either P+ or P- condition. Lines selected for P- were different from those selected for P+, and some lines selected for both P- and P+ felt at different yield ranks. It was concluded that modified bulk method followed by line selection was effective to develop breeding lines adapted to P- or P+. For P-, the modified bulk and line selection should be conducted in P-, whereas for P+, the modified bulk could be planted on P+ or P-, but the line selection should be conducted on P+ condition.