In the recently developed self-consistent-local composition (SCLC) theory (Ananth and Ramachandran, 1990) the osmotic and activity coefficients in single electrolyte solutions are expressed as sums of several independent contributions. In the present work, the approximate proportionality between certain pairs of these contributions is identified and the model is reformulated with fewer and more orthoganal parameters. The numerical difficulties experienced with the original model in the evaluation of parameters and in the extension of the calculations to mixed electrolyte systems are thus eliminated. The simplified model is shown to correlate the activity and osmotic coefficient data of large number of single and those of mixed electrolyte systems with good accuracy. The osmotic and activity coefficient of single electrolyte solutions are expressed in terms of two binary adjustable parameters and mixed electrolyte systems containing two salts and one solvent are expressed in terms of only one adjustable parameter in addition to the binary parameters determined from the component single electrolyte systems. The theory contains no additional adjustable parameters in the case of multielectrolyte (more than two salts) systems. The model is found to represent satisfactorily the behavior of electrolyte solutions at different temperatures with a single set of temperature-independent parameters.