Aim. Improving methods for increasing the efficiency of obtaining callus cultures and somaclones of flax (Linum usitatissimum L.) in vitro. Methods. Hypocotyl segments were cultured on Murashige and Skoog nutrient medium supplemented with sucrose (30 g/l) and phytohormones at various concentrations. Other conditions: photoperiod 16 hours, illuminance 2500 lx, relative humidity 60–80%, air temperature 22–24°C. Results. The ability to form callus and somatic embryogenesis of flax depends on the phytohormonal composition of the nutrient medium, the size of the explants and the distance between them. Conclusions. For intensive callus formation and somatic embryogenesis in vitro, the optimal concentrations of BAP (mg/l) can be expressed as 1.0 ≤ BAP ≤ 1.75; the optimal concentrations of BAP for the medium supplemented with NAA (0.05 mg/l) 0.5 ≤ BAP ≤ 2.0; the optimal concentration of NAA for the medium supplemented with BAP (1.0 mg/l) 0.025 ≤ NAA ≤ 0.150; and the optimal concentrations of IAA for the medium supplemented with BAP (1.0 mg/l) 0.05 ≤ IAA ≤ 0.50. Addition of 0.5 mg/l GA3 to the medium with NAA and BAP is effective. It is optimal to use hypocotyl explants 3–6 mm long and place them at a distance of 1.5–2.5 cm from each other. Organogenicity of callus is significantly reduced in the process of subculturing.