The effect of polyethylene glycol (PEG) treatments on somatic embryo production in Cryptomeria japonica was investigated. Embryogenic cells without PEG proliferated actively but most proembryos did not further develop beyond the pre-cotyledonary stage. However, the addition of PEG in the medium stimulated maturation of somatic embryos resulting in developing normal embryos.The best result was achieved on EM medium containing 50 g l^-1 maltose, 2 g l^-1 activated charcoal, 100 µM abscisic acid, and 20% PEG 6,000 (av. Mol. Wt.: 7,500). More than 360 somatic embryos per Petri dish were obtained after about 8 weeks in vitro culture. The frequency of germination and subsequent normal plant development were 40% and 36%, respectively. Growth of regenerated somatic plants has been monitored in the field.