Six of nine nonnative boreal conifers in three genera (Abies, Larix, and Pinus) regenerated in 11 to 31 years after they were introduced to mainland Alaska. Lodgepole pine (Pinus contorta var. latifolia Engel.) and the Siberian larches (Larix sibirica Ledeb. and L. sukaczewii N. Dyl.) were the most widely introduced species and will likely be the first nonnative conifers to naturalize. Siberian larch grew up to six times more stem volume than white spruce in the first 40 years on upland sites, but was susceptible to the larch sawfly and a blue stain pathogen carried by bark beetles. On productive sites, lodgepole pine appeared to grow more stem wood than white spruce for about 35 years after planting. Snowshoe hares and moose were the most serious pests of the nonnative conifers. Balsam fir (Abies balsamea (L.) Mill.) was the only species to regenerate in an established moss understory. Growth and age relationships were negative for all adequately sampled nonnative conifers and positive for native white spruce (Picea glauca (Moench) Voss). Data were insufficient to assess niche availability for commercial use of productive nonnative conifers in mixed stands in Alaska. Survey results indicate that introduction and naturalization of noninvasive tree species may improve the diversity, stability, and productivity of managed forest ecosystems.