This article completes the analysis of high-temperature mutual solubilities of hydrocarbons and water. Part I (Tsonopoulos and Wilson, 1983) presented benzene, cyclohexane, and n-hexane, while Part II (Heidman et at, 1985) extended the investigation to ethylbenzene, ethylcyclohexane, and n-octane. Part III presents experimental data up to the three-phase critical end point for C-6, C-8, and C-10, 1-alkenes, n-decane, n-butylcyclohexane, m-diethylbenzene, p-diisopropylbenzene, cis-decalin, tetralin, 1-methylnaphthalene, and 1-ethylnaphthalene. The thermodynamic analysis of Henry’s constants for hydrocarbons in water is extended to the critical temperature of water, while the solubility and volatility of wafer in hydrocarbons are successfully correlated with several modifications of the Redlich-Kwong equation of state.