Four small trees, 2 to 6 cm tall, were produced from shoots initiated on roots growing from callus tissue of tetraploid European aspen (Populus tremula L.). Firm white callus was initiated in the dark, at 27°C, on a modified Wolter and Skoog defined medium supplemented with amino acids and nucleotides. After 23 bimonthly passages, some inocula were transferred to medium made without auxin, kinetin, or supplements but containing 0.05 mg/liter 6-benzylaminopurine (BAP). Shoots were produced both from callus tissue and roots growing from callus; these shoots rooted and were isolated as independent and normal plants. A method of proliferating and rooting excised shoots is also given. Forest Sci. 17:348-350.