Abstract: Interactive effect of inorganic fertilizer and sewage sludge on nitrogen nutrition and growth of wheat was studied. Nitrogen was applied as 15N-labelled (NH4)2SO4 at 0, 50 , 150, and 300 mg pot–1 in all possible combinations with 0, 16, 24, 32, and 64 g pot–1sewage sludge (SS). Fertilizer N had no significant effect on the dry weight of roots. The above-ground plant components responded positively to the application of both fertilizer N and SS. The positive effect increased with the rate of application. In absence of SS, grain yield increased from 4.8 g pot–1 in the control to 10.6 g pot–1 at the highest level of fertilizer N. Likewise, the increase in grain yield due to different treatments ranged between 97 and 233% as compared to 23.3 and 82.5% recorded for straw component. The trends in N content of different plant components were fairly similar to those observed for dry matter yield and a significant correlation was observed between two parameters. Combination of both treatments at highest rate resulted in 127% increase in the total N yield of the plants. The contribution of N fertilizer to the total N content of the whole plant and its components remained fairly low and ranged between 11 and 45% in different treatments. The percent fertilizer N uptake (%FNU) varied from 22.6% at the highest level of application in the absence of sludge to 79.4% at the lowest level of application and in the presence of highest amount of SS. Fertilizer N uptake increased with the amount of SS; the extent of increase being more at the lower level of fertilizer N. Application of SS significantly improved the amount of unlabeled N determined in plants, with maximum effect being observed at the highest level of application. A part of this increase was due to N uptake from SS itself, while a substantial amount could be derived from the soil organic matter.