Application of Microcoleus vaginatus, a blue-green alga(Cyanobacterium) at different levels along with Meloidogyne incognigta, second state larvae, in the rhizosphere of tomato plants; showed that the plant growth as well as yield of tomato were increased and gall formations and nematode populations decreased with the increase in inoculum level of M.vaginatus. An inoculum level of 20 ml endospores suspension of M. vaginatus (2.4$ imes$ $10^6$ endospores per mol) per plant was optimum to reduce nematode attack with a population density of 1000 larvae per kg soil. Plant growth and yield of fruits were greatly suppressed and gall formations on roots, and nematode populations in soil were increased when M. incognita larvae five days prior to M. vaginatus inoculation. On the other hand, when . vaginatus inoculated ten days before nematode inoculation, suppressive effect of M. incognta on plants was reduced and their population density as well as gall formations were also decreased significantly. The efficacy of simultaneous inoculation of both nematode and M. vaginatus was lied in between two treatments discussed above.