In this work the investigations of water vapour adsorption and calculation the specific surface area of soil samples of Sudanese Vertisols in North (NG), Central (CG) and South (SG) Gezira are presented. The Brunauer-Emmet and Teller (BET) equation was used to analyze experimental adsorption data of water vapour and to calculate the specific surface area (SBET) from both the adsorption and the desorption branches of the adsorption isotherm. The values of the SBET estimated from the adsorption isotherms ranged from 106 to 120, from 141 to 155 and from 165 to 187 m2 g-1 for the soil from North, Central and South Gezira, respectively. If the desorption isotherms were used, the ranges of SBET were 117-140, 158-183 and 179-206 m2 g-1, respectively. Linear regression plot for the electric conductivity (EC), soluble Na+ ions and the difference DS=S(des)-S(ads) was found. The specific surface area slightly increased with the depth of the soil profile. The specific surface area of Vertisols from Sudan increased from the north to the south and was related to the water regime and the intensity of cracking. The correlation between selected chemical and physical characteristics of soils and the values of the specific surface area was found.