Pot experiments were designed in two seasons of 2004 -— 2005 to study nutritional status of onion as affected by biological control of white rot disease. The experiments involved three different microorganisms, namely Bacillus subtilis, Tnbhoderma harzianum and mixture of Mycorrhiza glomus of fungi Efun'cafum glornus in Traradices glomus fasciculatum, alone (individual bioagents) or together (mixture bioagents), which were used as soil drench. Two doses of B.sublilis and iiharzr'anum, namely (A) 100 and (B) 50 mL l kg soil and two doses of Mycorrhlza namely, (A) 10 and (B) 5 glkg soil were applied. The obtained results can be summarized as follow: 1. Application of microorganisms, namely (Bacillus sublilis, Trfchoderma harzianum and Mycorrniza glomus at the rate A or 8 increased the availability of macronutrients ( N, P and K) in soil, macronutrients uptake, percent yield, efficacy of control white rot disease as compared to control treatment (without inoculation). 2. Application of microorganisms at the rate (A) was superior in all parameter under study to rate (B). 3. At a scale of single treatment application of Bacfllus subtilis as individual to soil was superior in % efficacy of control white rot disease, N, P and K uptake, availability N, P and K in soil and percent yield than other microorganisms. 4. The mixture of Bacilus subtllis and Mycorrhr'za glomus gave the highest increases in all parameters than those achieved by the mixture of Trfcrroderma harzranum and Mycorrhiza glornus or any single treatment. 5. Application of a mixture of Bacillus subfilis and Mycorrhiza increased the % of efficacy of control white rot disease.