A chemical tissue test method, designed to determine the mineral status of field crops, which has been tested to diagnose mineral deficiencies in potato and cauliflower, is described. The procedure comprises a specialized method of sampling fresh plant material, followed by the extraction of the easily soluble nutrients from selected portions of the plants and their subsequent estimation by colorimetric and turbidimetric tests. A buffered solution consisting of glacial acetic acid and sodium acetate (100 gm. sodium acetate and 30 ml. of glacial acetic acid in 1 litre of distilled water, at pH 4.8) is used for the extraction of the nutrients from weighed amounts of fresh tissue for a standard time, viz. 15 minutes. The tissue extract is tested for potassium, magnesium, calcium, phosphorus, nitrate nitrogen and manganese. The detection of the last at deficiency levels involves the use of specially purified reagents. Nutrient standards for the various elements have been fixed for a number of plants and threshold deficiency values are given which coincide with the development of visual symptoms of the respective deficiencies. It is shown that the tissue test data reflect manurial and cultural treatments and are in accord with results of the visual method and those of ash analysis of the plants. The method is recommended as complementary to visual diagnosis for determining deficiencies in field crops and as a quick procedure for assessing the mineral status of plants. It replaces the time-consuming process of ash analysis.