Above-ground biomass, annual production, and leaf area index (LAI) were estimated for several years in aspen stands aged 6, 15, and 52 years old in 1968. Based on regressions of dry weight on stem diameter, biomass (stems and branches) estimates for 1968 were 21 500 kg ha−1in the juvenile stand, 51 200 kg ha−1in the intermediate stand, and 91 800 kg ha−1in the mature stand. Net annual above-ground production (stems and branches) for these stands in 1968 was 6900, 7000, and 1340 kg ha−1respectively. In 1969, foliage amounted to 2600, 2600, and 1500 kg ha−1, providing LAI of 2.4, 2.9, and 1.6 for the stands. Net assimilation rates were roughly 20, 17, and 9 g m−2week−1.Aspen stands regenerated as suckers may attain maximum annual production within a few years, coincident with the development of maximum LAI.