To study the possible use of phytase and yeast (Saccharomyces cervisiae) in corn-soy bean meal base diet with different levels of available phosphorous in Arbor Acers broiler chicks, an experiment was conducted with 264 day old chicks of an average weight of 44.6 grams each. A completely randomized design of 6 treatments and 4 replications (11 chicks per replicate) for periods of starter, grower as well as for the total period of feeding system was employed. Experimental diets were balanced to contain equal levels of energy and protein but available phosphorous concentration differed for control diet which was based on NRC recommendation while for other diets, it was 50 percent below NRC recommendations. Other nutrients were balanced on the bases of energy concentration levels. Treatments were T1) control, T2) control + 500 units of phytase + 0.1 percent yeast, T3) control diet containing 50 percent available phosphorous according to NRC recommendations, T4) control diet containing 50 percent available phosphorous (NRC recommendation) + 0.1 percent yeast, T5) control diet containing 50 percent available phosphorous (NRC recommendation) + 500 unit phytase, T6) control diets containing 50 percent available phosphorous (NRC recommendation) + 500 unit phytase + 0.1 percent yeast. Daily feed intake, live weight gain, feed conversion ratio, calcium and phosphorous concentrations of blood serum were assessed. Results indicated that the decrease in available phosphorous by 50 percent in control diet (T3) caused a significant decrease in feed intake and live weight gain in comparison with respect to control [either with or without phytase and yeast (P<0/05)]. The most suitable FCR was obtained in control (T1) and use of phytase and yeast in control diet (T2) while control diet containing 50 percent available phosphorous (T3) exerted no effect on FCR. Concentrations of blood serum calcium were similar in all diets but phosphorous concentration during periods of 21 and 42 in control diets [containing 50 percent available phosphorous (T3, T4, T5 and T6)] significantly (p<0.05) decreased in comparison with control diet along with phytase and yeast (T2). The overall results indicated that the use of phytase and yeast in control diets and in control diets plus 50 percent content of available phosphorous are not recommended.