Among the micronutrients, boron has the greatest impact on the yield quality and quantity. In case of boron deficiency, problems can be detected in flower formation and fertilization, furthermore, carbohydrate and lipid formation is also inhibited. As a secondary consequence, the strength of cell walls also decreases, which increases the susceptibility of the plant to diseases (mainly to those caused by microorganisms). In order to ensure a proper boron supply of plants, the available boron content of the soils should be determined punctually. Presently, the mostly used method for determining the boron content is the classical hot water extraction method of BERGER and TRUOG (1939, 1940). A great disadvantage of this method is that its application is limited, because it is not suitable for performing series of examinations. Therefore, our research objective was to develop an extractant for determining the available boron content of soils in order to substitute (or to be used simultaneously with) the hot water extraction method. For the examinations, extremely different soil samples were collected. The samples were from the following soil types: acidic shifting sand, sand with high carbonate content, humus sand, brown forest soil with alternating thin layers of clay ("kovárvány"), brown forest soil (Ramann-type), brown forest soil with clay illuviation, calcareous chemozem, leached chemozem, chemozem meadow, typical meadow, chemozem-like meadow, marshy meadow, meadow solonetz and solonchak-solonetz soils. When selecting the 50 soil samples, the aim was that they should represent the widest possible range as regards the soil parameters and the expected boron content so that the soil extractants could be applied on the most extreme soils. The hot water soluble boron content of the 50 soils ranged between 0.28 and 1.76 µg/g. Similar values were measured in hot 0.01 M/dm³ CaCl₂ solution of neutral pH (0.30 and 1.73 µg/g boron). A lower amount between 0.08 and 0.97 µg/g could be extracted at room temperature by using 1.0 M/dm³ (pH=4.8) ammonium acetate solution. The 0.01 M/dm³ CaCl₂ solution extracts only a small portion of the soil's boron content at room temperature, no boron could be detected in the acid sandy soils deficient in boron, while from the chemozem and meadow soils of high boron content only a maximum of 0.14 µg/g boron could be extracted. The amount of boron extracted with 0.5 M/dm³ NaHCO₃ solution (pH = 8.5) was between 0.20 and 1.80 µg/g. The tightest correlation was found between the hot water (x) and the hot 0.01 M/dm³ CaCl₂ solution (y) (r = 0.982 ***). Based on the regression equation the amounts of the extracted boron can be considered practically equal: y = 0.98*x + 0.001. A tight correlation was also found between the boron contents extracted by hot water and room-temperature ammonium acetate(r = 0.792***). The regression equation shows that the ammonium acetate extracts half as much boron from the soil as hot water: y = 0.499*x – 0.010. However, the correlation between the boron contents soluble in hot water and sodium hydrogen carbonate was weak (r = 0.161 n.s.). The obvious explanation is that the dissolution of the humus materials inhibits the correct boron analysis. The results indicate that the hot water boron extraction method can be substituted by the ammonium acetate method. In order to determine the threshold limits, presently pot experiments are being performed. The research was carried out with the support of the Hungarian Scientific Research Fund (OTKA T 043410).