Abstract One-month-old soybean ( Glycine max [L.] Merrill), cultivar ‘Williams’, plants were exposed to nitrogen dioxide (0·1, 0·2, 0·3 and 0·5 ppm) and carbon filtered air (control), 7 h per day, for 5 days, under a controlled environment. Leaf chlorophyll content (Ch a, Ch b, and total Ch content) and foliar nitrogen content (%N) were determined before and after the exposure. The influence of NO 2 treatments up to 0·3 ppm on leaf chlorophyll content was negligible although a stimulatory effect was evident in Ch a and total Ch content with 0·2 ppm NO 2. Marked decline in Ch content was observed with 0·5 ppm treatment; the reductions in Ch a and total Ch were 45% and 47%, respectively. Foliar-N contents of plants treated with 0·2 and 0·3 ppm NO 2 were higher than the control; plants exposed to 0·5 ppm NO 2 showed a 41% reduction in foliar-N compared to pre-exposure values.