Oxyfluorfen spraying resulted in distinct lowering of nitrate reductase with both doses of the herbicide (5 ppm and 15 ppm) and in both roots and leaves of maize seedlings throughout the run of the experiments. After 5 days of spraying, diminishment of the enzyme amounted to 37% and 56% with the lowest dose of the herbicide in roots and leaves respectively. A similar pattern was observed after 10 and 15 days of spraying. On the other hand, the nitrate content behaved similarly indicating induction of nitrate reductase by nitrate availability. Lowering of nitrate reductase and nitrate content by oxyfluorfen treatment could be attributed to decline in carbon assimilation by some herbicides as verified by several workers, and nitrate uptake and reduction to nitrate reductase are energy expending processes.