The ability of hairy vetch (Vicia villosa Roth) residue (100 g/plant) to supply N and to increase yields of tomato (Lycopersicon esculentum Mill.) was compared with that of N fertilization (0, 4.1, and 8.2 g/plant N) in a medium containing a mixture of 3 perlite: 1 vermiculite in a greenhouse and a lathhouse. Hairy vetch residue did not interact with N fertilization in affecting tomato yield and medium N concentration. In the greenhouse, leaf dry weight, leaf and stem N uptake, total (fruit + stem + leaf + root) dry weight and N uptake of tomato, and NH4+ and inorganic N concentrations in the medium at transplanting were significantly greater with than without residue. In the lathhouse, fruit number, fresh and dry yields and N uptake, leaf, stem, and root dry weights and N uptake, root length, total dry weight and N uptake of tomato, and NH4+, NO3-, and inorganic N concentrations in the medium at transplanting, and inorganic N at harvest were greater with than without residue. Nitrogen fertilization increased fruit number, fresh and dry yields and N uptake, stem, leaf, and root dry weights and N uptake, root length, and total dry weight and N uptake. The residue was as effective in increasing fresh fruit yield, total dry weight, and N uptake as was 4.4 to 7.9 g/plant of N fertilizer. Tomato yield and N uptake per unit amount of N supplied was greater for the residue than for N fertilization, suggesting that hairy vetch residue can be effectively used as N fertilizer for tomato production.