A field experiment was conducted at the G.B. Pant University Research Station, Ujhani (U.P.) in rainy (Kharif) season of the year 1994-1995 to study the effect of Rhizobium, VAM (vesicular arbuscular myc- orrhiza) and PSB (phosphate solubilizing bacteria) inoculation, with and without P, on blackgram (Vigna mungo L.) seed yield. Phosphorus application in soil with medium P content (5.4 mg kg～1) increased nodu- lation, grain yield, N and P in plant and grain over no phosphorus control. Forty kilograms of P-2O-5 each hactare recorded an increase of 20.6 % in nodule dry weight, significant increases of 0.35 g kg～(-1) in N con- centration and 1.28 g kg～(-1) in P concentration of plant over 20 kg P-2O-5 ha～(-1). Similar significant increases of 0.59 g kg～(-l) in grain yield and 0.54 and 0.23 g kg～(-1) in N and P concentrations of the grain, respectively, over 20 kg P-2O-5 ha～(-1) were also obtained with higher dose. Inoculation of Rhizobium ＋ VAM ＋ PSB at all the stages of plant growth recorded maximum increases in all the parameters studied. Dual inoculation of Rhizobium with either VAM or PSB was generally significant in the effect and better than that of VAM ＋ PSB, however, P accumulation in plant and grain was more with VAM ＋ PSB. Among single inocula tions, Rhizobium gave highest and 21.0 % more nodule number, 34.7 % more nodule dry mass, 0.73 g kg～(-1) more N in grain and 4.2 % higher grain yield over PSB. PSB, however, registered significant increases in P concentration in plant and grain over VAM and Rhizobium. A field experiment was conducted at GB Pant University Research Station, Ujhani (UP) in rainy (Kharif) season of the year 1994-1995 to study the effect of Rhizobium, VAM (vesicular arbuscular myc orrhiza) and PSB (phosphate solubilizing bacteria ) inoculation, with and without P, ​​on blackgram (Vigna mungo L.) seed yield. Phosphorus application in soil with medium P content (5.4 mg kg ~ 1) increased nodu- lation, grain yield, N and P in plant and grain over no phosphorus control. Forty kilograms of P-2O-5 each hack recorded an increase of 20.6% in nodule dry weight, significant increases of 0.35 g kg -1 in N con- centration and 1.28 g kg -1 Similarity increases of 0.59 g kg ~ (-1) in grain yield and 0.54 and 0.23 g kg ~ (-1) in N and P concentrations of the grain, respectively, over 20 kg P-2O-5 ha ~ (-1) were also obtained with higher dose. Inoculation of Rhizobium + VAM + PSB at all the stages of Plant growth recorded maximum increases in all the parameters studied. Dual inoculation of Rhizobium with either VAM or PSB was generally significant in the effect and better than that of VAM + PSB, however, P accumulation in plant and grain was more with VAM + PSB. Among single inocula tions, Rhizobium gave highest and 21.0% more nodule number, 34.7% more nodule dry mass, 0.73 g kg -1 more N in grain and 4.2% higher grain yield than PSB. in P concentration in plant and grain over VAM and Rhizobium.