The effects of NH*:N03 ratio on growth, water uptake, solution pH, mineral nutrition and yield of tomatoes were investigated using the nutrient film technique. There were six NH*:N03 ratios: 0:100 with and without pH control; 12.5:87.5, 25:75, 37.5:62.5 and 50:50 without pH control. There was an increase in pH of the nutrient solution with 0:100 and 12.5:87.5 ratios, but the pH decreased with 50:50 ratio. Higher NH+:N03 ratio reduced leaf and root growth. The reduction in leaf and root growth could be attributed to reduction of plant water uptake. Fruit fresh weight was reduced and the percentage of blossom-end rot increased with higher ratio of NH+:N03 in the solution. Increased ratio of NH4+:N03 increased N content and decreased Ca content in all the plant tissues. P, K and Mg content decreased in leaf tissue with increasing NH*:N03 ratio.