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Spent mushroom compost (SMC) was obtained from Ralston Purina Mushroom Plant in Loudon, Tennessee to determine its effects as a soil amendment for growing vegetables under field conditions. Four rates (0, 2, 10, and 20 kg/m2) of SMC were applied to a Sequatchie fine sandy loam in 1981 and 1982. Yields of cabbage, cucumber, mustard, onion, radish, snap bean, spinach, and tomato were evaluated. Spent mushroom compost application decreased the bulk density, increased the percentage of small pore space, pH, and electrical conductivity. Within the year of 1981 or 1982, the difference in the response of vegetable yield to SMC application was probably due to the difference in ability of each vegetable species to tolerate salinity. Difference in the yield response of the same vegetable species to SMC application between the two years of test period was perhaps because of the combined effects of salinity, climatic conditions, and the residual effect from the first year's application of SMC. All vegetables tested in both years had significantly increased potassium concentration, but decreased magnesium concentration in leaf tissue. Under greenhouse conditions with adequate watering and leaching, snap bean, cucumber, radish, spinach, and tomato were grown from seed in soils amended with 0, 10, 20, 30 and 50% of SMC. The percentage of seedling emergence was not affected while the rate of seedling emergence was delayed by the addition of SMC. Optimum seedling growth was observed at 30% or 50% of SMC. The elemental content in seedling tissue indicated a potassium and calcium and/or magnesium antagonism in ion uptake. Under greenhouse conditions with a non-leached system, vegetables grown at 50% of SMC exhibited some stunting. The increased plant growth and yield were obtained with addition of 20% to 30% of SMC. In general, using SMC as a soil amendment was beneficial to some vegetables, but its high soluble salt content could make excessive rates or long term use harmful to plants that are sensitive to salinity.