On the supposition that liquid is composed of a mixture of microcrystallites and vacancies, and on the basis of significant structure theory and analysis of the radial distribution function of liquids, a new two-parameter model is presented for correlating thermal conductivities of liquids and liquid mixtures. The thermal conductivities of inorganic compounds, paraffins, olefins, cycloparaffins, aromatic hydrocarbons, alcohols, ethers, aldehydes, ketones, esters, organic acids and some refrigerants over wide ranges of temperature are calculated using the new model and compared with data reported in the literature. The method is extended to mixtures by using simple mixing rules. Calculated results show that the new model can be used for the correlation of the thermal conductivities of systems consisting of nonpolar and polar compounds and also for those of aqueous solutions. Especially, for pure compounds such as inorganic compounds, nitrogen- or sulfur-containing materials and aldehydes, and for mixtures consisting of alcohols and aqueous systems, the proposed correlation shows better agreement with experimental data than the models recommended by Reid et al. (1987, The Properties of Gases ann Liquids, 4th Edition. McGraw-Hill, New York).