Published biomass equations were applied to sample trees from an 18-year-old Populus tremula (L.) x P. tremuloides (Michx.) (Astria) stand in Germany and compared with the measured dry weights. Equations originally developed for quaking aspen did not perform better than equations derived from European aspen data. The complexity of equations also did not influence the mean percent deviation of calculated dry weights from measured dry weights. Equations derived from measurements in short-rotation coppice cultures grossly overestimated weights. The accuracy of the predictions of total tree biomass changed according to the gradient in height:diameter ratio of the sample trees of the original studies. Equations from trees with similar h/d ratio as the sample trees were more accurate than others. When equations from the literature are used to estimate biomass for given stands, equations that resulted from sample trees with similar height:diameter ratios should be preferred. (c) 2007 Elsevier Ltd. All rights reserved.