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Municipal sewage sludge, also termed "biosolids," has been shown to be an excellent soil conditioner for the reclamation of mine tailings. A large-scale (approximately 30 ha) field experiment on the Kennecott Utah Copper Corporation mine tailings impoundment, west of Salt Lake City, Utah, USA, demonstrates the usefulness of biosolids to improve vegetative growth in a difficult, semi-arid environment. Relatively few such studies have been performed in the semi-arid climate that is typical of the state of Utah. Rainfall averages about 36-cm yr(-1) in the Salt Lake valley. Two types of biosolids were used in the project: anaerobically digested and aerobically treated, alone or with limestone and wood residues, as secondary treatments. Biosolids were applied at four application rates: 0 (as a control), 11.2, 22.4, and 33.6 Mg ha(-1) on a dry solids basis. Results from the first year of the study show that biosolids were successful in enhancing plant biomass and areal cover without a significant increase in tissue metal concentrations in the planted species. Biomass increased from 43.0 g (m(2))(-1) in the control plots to a maximum of 554.4-g (m(2))(-1) when 33.6-Mg ha(-1) of biosolids were applied. The total areal cover increased significantly from 7.3 % at 0-Mg ha(-1) to 62.8 % at the 33.6-Mg ha(-1) biosolids application rate. There were no differences in metal concentrations in plant species from the control and biosolids-amended plots, and with few exceptions all metal concentrations were below phytotoxic levels.