In an acid forest soil of pH 4.0 to 4.2 amended with glucose, 1.0 mug of nitrite-N per g of soil inhibited the rate of O(2) utilization and CO(2) evolution. The inhibition was evident only for several hours after nitrite addition, and the subsequent rate of glucose mineralization was the same as in soil not receiving nitrite. The decomposition of protein hydrolysate was reduced by 10 mug of nitrite-N per g of soil but not lower concentrations, and the inhibition of this process by 20 mug of nitrite-N per g had dissipated after 24 h. Nitrite disappeared readily from this soil. More than 20 mug of bisulfite-S per g of soil was required to inhibit glucose decomposition. The data suggest that the possible antimicrobial effects of low levels of NO(2), which give rise to nitrite in soil, require further evaluation.