To compete with tree and row crops on California's prime agricultural lands, biomass yields may have to exceed 20 dry tons per acre per year at a market price of & 30 per dry ton. The results we report here for a selected clone of Eucalyptus camaldulensis (river red gum), grown in an intensively managed plantation at 2,719 trees per acre, suggest that the required yield can be exceeded by the third year after planting. A clone of E. grandis (rose gum) would probably give similar yields.