Competition for soil nutrients, moisture, and light was examined in 5-year-old plantations of young coastal Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco var. menziesii) growing at 17- to 123-cm spacings, alone or with either of two competitors, grass (Elymus spp. and Agrostistenuis L.) or red alder (Alnusrubra Bong.), on three different site types in the Oregon Coast Range. Douglas-fir foliar nitrogen concentration and total and available soil nitrogen did not differ significantly by competitor species; however, foliar phosphorus was higher in the grass treatments. Both foliar nitrogen and phosphorus concentrations were significantly lower at high planting densities. Predawn moisture stress varied with site, competitor, and density, the lowest stresses occurring at low densities where Douglas-fir was growing alone. Canopy light penetration varied with competitor, density, and height above ground, the lowest values occurring under the red alder canopy. Grass competed with Douglas-fir seedlings primarily for moisture until crown closure eliminated the grass. Nodulated red alder did not increase soil or Douglas-fir foliar nitrogen on any site or at any density, but competition from red alder trees reduced available light and moisture for Douglas-fir. Regardless of competitor type, high density resulted in increased demands on resources.