Suspension cultures initiated from callus derived from petiole explants of aspen hybrid (Populus tremuloides × P. tremula) produced somatic embryos. Callus was induced on a MS medium supplemented with 5 mg·L–1 2,4-D and 0.05 mg·L–1 zeatin under light conditions. Embryogenic calli were obtained when a subsequent subculture of calli was suspended in the same basal me-dium with 10 mg·L–1 2,4-D. The highest number of globular embryos were induced from embryogenic calli by cell suspension cul-ture in a MS liquid medium supplemented with 10 mg·L–1 2,4-D. Genotype and 2,4-D concentration were vital to the induction of embryogenic calli producing competent cells. Embryogenic calli for each genotype were heterogeneous. Green calli with gel-like consistency could yield more competent cells than light yellow embryogenic calli. However, some globular embryos broke into slices and some developed abnormally after one month of culture under the same or other hormonal conditions. Suspension cultures initiated from callus derived from petiole explants of aspen hybrid (Populus tremuloides × P. tremula) produced somatic embryos. Callus was induced on a MS medium supplemented with 5 mg · L-1 2,4-D and 0.05 mg · L- 1 zeatin under light conditions. Embryogenic calli were obtained when a subsequent subculture of calli was suspended in the same basal me-dium with 10 mg · L-1 2,4-D. The highest number of globular embryos were induced from embryogenic calli by cell suspension cul-ture in a MS liquid medium supplemented with 10 mg · L-1 2,4-D. Genotype and 2,4-D concentration were vital to the induction of embryogenic calli competent competent cells. Embryogenic calli for each genotype were However, some globular embryos broke into slices and some accommodating abnormally after one month of culture under the same or other hormonal conditions.