Callus cultures were induced on mature embryo mesocotyl explants in Hordeum vulgare cv. Zafer-160. The callus induction ratio was 54% in Murashige-Skoog (MS) medium supplemented with 1 mg 1(-1) 2,4-dichlorophenoxyacetic acid (2,4-D). After transfer at 22, 45, 360, 540 days of culture to MS medium containing lower concentrations of 2,4-D (0.5, 0.1, 0.01 mg 1(-1)) or MS medium lacking 2,4-D, 45-day-old callus cultures showed somatic embryogenesis. The optimum 2,4-D concentration for somatic embryogenesis was 0.01 mg 1(-1). Callus cultures of 360 days showed regeneration via both somatic embryogenesis and organogenesis under the same conditions. Abnormalities in both number and structure of chromosomes increased with the age of calli. This phenomenon might be related to the loss of regeneration ability in 540-day-old calli. In-vitro regenerated plantlets gave rise to normal-looking plants after their transfer to soil. Regenerated plants had the normal diploid chromosome number (2n = 14) in their root tips.