This paper deals with investigations on nitrate determination with a nitrate-specific ion electrode. Analytical results for the nitrate content in soil extracts are compared with analyses carried out by two colorimetric methods. The extracting agents used are 0·02 N copper sulphate, 2 N potassium chloride and distilled water. Results for nitrate determinations in soil suspensions and corresponding filtrates are also compared.The stability of soil extracts, the influence of variation in the ratio of grams of soil to millilitres of extracting agent and in the shaking time, interferences caused by ionic strength and anions, accuracy and reproducibility are also discussed.The investigation shows that nitrate determination with the electrode is reliable both for soil extracts and for soil suspensions. The determination is rapid, and the interferences are not serious.