A report is given of several theoretical expressions based on mass transport phenomena that relate the radioactivity escaping from such solids to diffusion, dissolution processes, surface conditions, and radioactive decay. Representative available data for radioactive waste solids incorporated in cement, asphalt, ceramic, and glass media are analyzed using the theoretical expressions presented. These analyses show that an expression taking into account diffusion and concentration-dependent dissolution gives good agreement with the data for most of the products considered. In the main, these products can be categorized as waste solids of low solubility incorporated in inert matrices. The effective diffusivities obtained are in the range of mid 10$sup - 17$ to mid 10$sup -12$ cm$sup 2$/sec, the dissolution rate constants are in the range of high 10$sup -9$ to low 10$sup -7$ sec$sup -1$, and the surface transfer constants are in the range of low 10$sup -4$ to low 10$sup -3$ sec$sup -1$ for the products analyzed. Once determined, such parameters can be used to compare various waste products and to estimate releases from these products, in particular, long-term releases. (auth)