Spinach was grown in the greenhouse in soil with the pH adjusted to 5.0, 5.5, 6.0, 6.5, and 7.0, N fertilizer rates of 0, 50 and 200 mg N/Kg soil, and Mo fertilizer rates of 0, 0.3 and 1.2 mg Mo/Kg soil. The NO3‐N concentration of the tissue increased with fertilizer N or a rise in pH from 5.0 to 7.0. The addition of Mo at either rate reduced the NO3concentration of spinach grown at pH 5.0 and 5.5 but had no effect on plants grown at pH 6.5 or 7.0. At pH 6.0 the 1.2 mg Mo/Kg soil rate was effective at the 50 and 200 mg N/Kg soil fertilizer rates but had no effect on spinach grown without a N application. At the same pH, the 0.3 mg Mo/Kg soil rate had no effect on NO3content of spinach grown with the 50 mg N/Kg rate but did reduce the NO3content of spinach grown without N added or with the 200 mg N/Kg soil. The 1.2 mg Mo/Kg soil rate was more effective than 0.3 mg Mo/Kg rate in reducing NO3content of spinach grown with 200 mg N/Kg soil at pH 5.0–6.5 inclusive but gave variable results when no N or 50 mg N/Kg soil was added. Molybdenum did not affect the total N or NO2concentrations of the plants.