Data on the densities of organic compounds is essential for both scientific and industrial applications. Knowledge of densities is important in many areas, including custody transfer of materials, product specification, development of various predictive methods, and for characterizing compounds and estimating their purity. The densities of monocyclic hydrocarbones are collected from the original literature published from 1870 to early 1996 and were critically evaluated. The tables contain the original literature data along with their estimated uncertainties, and the evaluated data, in both numerical form and as coefficients to equations with selected statistical information. The volume also contains the CASR Number Index, a Chemical Name Index and a CD-ROM which allows fast full text index search.