Two pot experiments were simultaneously conducted during the early summer seasons of 1997 and 1998. The first experiment studied the effect of four initial population (P_i) densities of Meloidogyne incognita (0, 4 ´ 10³, 10 ´ 10³ and 20 ´ 10³ nematode eggs/pot) on growth and yield of susceptible (Castlerock) and resistant (F₁ hybrid Heinz 2710) tomato cultivars. The susceptible cv. was greatly suppressed by M. incognita in most growth and yield parameters, viz., stem length, number of leaves, leaf fresh and dry weight, root fresh weight, chlorophyll and N, P, K content of leaves, fruit yield per plant and average fruit weight. Meanwhile, the resistant cv. was slightly affected. On the other hand, titratable acidity and vitamin C and T.S.S. content of fruits were higher in the susceptible cv. Final nematode population (P_f), root gall index and reproduction factor (R_f) were significantly higher in the susceptible cv. as compared with the resistant one. A negative relationship was found between P_i and most vegetative growth parameters, where gradual decreases were observed with the increase in P_i. However, a positive relationship was found between root fresh weight and P_i. Fruit yield per plant decreased with the increase in P_i. Average fruit weight significantly decreased at P_i 20 ´ 10³ as compared with the control. Fruit acidity and vitamin C content decreased at most P_i levels. P_f increased with the increase in Pi level. Root gall index ranged from 0.0 in the control to 5.0 in the various inoculum levels used. R_f  increased with the increase in P_i up to 10 ´ 10³. The interaction between tomato cultivar and P_i had a significant effect on leaf fresh weight, leaf chlorophyll content and fruit yield per plant, where the 0.0 level with the resistant cv. had the highest records. However, this treatment had the lowest root fresh weight. The lowest P_f was obtained when the 4 ´ 10³ level was used with the resistant cv. Root gall index was only slightly affected by the P_i level in the resistant cv., but was greatly affected in the susceptible one. The lowest R_f was obtained when the 20´ 10³ level was used with the resistant cv. The second experiment studied the efficacy of four organic manures (rabbit, pigeon, cow and poultry) in controlling M. incognita in tomato. All organic manures improved most plant growth and yield parameters, i.e., stem length, number of leaves, leaf fresh and dry weight, root fresh weight, leaf chlorophyll and N, P, K content, fruit yield per plant, average fruit weight, and fruit acidity and vitamin C and T.S.S content. Applying pigeon and poultry manure increased these parameters more than rabbit or cow manures. All organic manures suppressed P_f, root gall index and R_f. However, pigeon and poultry manures caused more suppression in root gall index and R_f and pronounced increase in nematode reduction % as compared with cow and rabbit manures.