Experiment was conducted on 64 broiler chickens from 0 to 18 days of age to evaluate phosphorus availability from lupin and field bean. As indicators, bone mineralization and breaking strength and the retention of P fractions were used. Body weight at 18 days of life was reduced (P<0.01) when P deficient semi-synthetic diet without inorganic P (P0) was fed. Femur ash content and tibia breaking strength were lowest and similar in chickens fed P-deficient (P) and field bean containing (BP0) diets. Their femur ash content and tibia breaking strength were lower by about 12% (P≤0.05) and 45% (P<0.01) than of chickens fed a diet with 0.2% of inorganic P (P2) which showed the best bone mineralization. Phosphorus was more available from lupin than from field bean (judged from breaking strength measurements: respectively 53 and 0% compared with inorganic P considered as 100% available). The results are discussed with respect to validity of the assays used and anti-nutritive factors in field bean.