The application of topsoil over phytotoxic mine waste materials is often the most effective method for establishing plant communities and protecting these communities from the inimical properties of such waste materials. However, long-term data on the effectiveness of this type of remediation, as well as on cultural treatments used to enhance vegetation establishment on topsoil cover treatments, are lacking. Therefore, we evaluated long-term plant community development on study plots where 60 cm of Paraho retorted oil shale was covered by various depths of topsoil. The study plots were drill seeded with native, introduced, or a combination of native and introduced species, and fertilized with one of three rates of nitrogen (N) and phosphorus (P) fertilizer following construction of the plots in 1977. Data collected 20 yr after seeding showed that total aboveground biomass was greatest on deeper topsoil depths and on plots seeded with introduced plant species. However, when considering the interaction between these two variables, we found that native species were as productive as introduced species on deeper topsoil depths and on the control. Relative plant species composition and plant species richness were greatly influenced by seed mixture treatments. Plots seeded with a particular seed mixture in 1977 were still highly dominated by those species originally seeded, and native seed mixture plots were more species rich than introduced seed mixture plots. Chemical analysis of the soil covers and underlying retorted shale suggests that leaching processes have moderated the once adverse chemical characteristics of the retorted shale.