This paper deals with the indirect estimation of the two main parameters of cohesive soils (swell percent and shear strength) that play an important role in the deformation of structures. While the literature contains several empirical techniques for assessing the swelling potential and shear strength, no satisfactory equations are available that provide an estimation of percent swell and shear strength based on liquidity index. In this study clayey soil samples were collected from five alluvial deposits in Turkey and parameters were determined including liquidity index, percent swell and shear strength. Regression equations established for the liquidity index-percent swell and liquidity index-undrained shear strength had high correlation coefficients of 0.87 and 0.95 respectively. It must be considered that the equations proposed in this paper were obtained from the soils having very low organic material and similar to 50% clay mineral content, a liquidity index range of -0.52-0.91. For wider and generalized application of the equations, the formulae would have to be tested over a data set with a larger range of liquidly index, organic material and clay content. However, the equations, derived from the samples used in this study, apply well with an acceptable accuracy to be used for percent swell and undrained shear strength estimations at the preliminary stage of site investigations. (C) 2009 Elsevier B.V. All rights reserved.