High potential productivity together with short rotation periods have made hybrid aspen an interesting option for wood production on former arable land in Nordic countries.In this study,some of the oldest active experi-mental plots with hybrid aspen in Sweden were remeasured at 23-30 years of age.A main aim was to assess age and productivity at the time of maximum mean annual volume increment.In addition,the influence of commercial thin-ning on stand development and differences in genetic gain among clones were investigated.Data from five experiments in southern Sweden were used,including three genetic trials,one demonstration stand with a clone mixture and one stand regenerated from root suckers.The three genetic trials were treated as single plot experiments,subject to a standard thin-ning program.In the remaining experiments,different thin-ning strategies were tested in a balanced block design.Vol-ume growth had culminated or was close to maximum at age 25-30 years.Mean annual stem volume increment at cul-mination was 20-22 m3 ha-1 a-1.Dominant height reached 30-35 m at 28-30 years of age.Mean diameter at breast height was 27-29 cm after 29-30 years in the genetic trials.Clonal ranking based on diameter at age 7-9 years was posi-tively correlated with the ranking at the final measurement in the genetic trials,20 years later.This indicates that clones can be selected for superior growth based on results from young trials.More intense thinning programs increased the mean diameter compared to light thinning.The study indi-cates that one or two early and relatively heavy thinnings can promote the development of crop trees,without jeopardizing total volume production during a rotation of 25-30 years.