In vitro seedlings of Lilium×formolongi Hort. cvs. Norikula, RaiZen No. 1, RaiZen No. 3, RaiZen Early, and Bailansa were used to induce callus by variously modified Murashige and Skoog (MS) media, using protocols for flask culture and bioreactor culture. Green embryogenic callus proliferated from roots near the base of bulblets of five varieties on media containing 0.53–5.3 μM α-naphthaleneacetic acid (NAA), and 28 cell lines were obtained by subcultures on the same medium. For flask culture, the fresh weight (FW) of embryogenic cell clumps doubled every 4 wk on MS basal salts supplemented with 0.53 μM NAA and 30 g l⁻¹ sucrose. The maximum frequency of somatic embryos that developed into plantlets was 76.67 ± 17% when plated onto solid MS basal medium without plant growth regulators (PGRs). Among the treatments using four types of bioreactors, the best cell growth and regeneration rate (74 ± 0.14%) of somatic embryos was in a modified 2-l bioreactor. Cells incubated in the other three bioreactors turned brown and died. Histological study revealed that regeneration was by somatic embryogenesis. The regenerants showed normal growth and flowering after 8–9 mo. in the field. A cell line of cv. Norikula has been subcultured in MS basal salts containing 0.53 μM NAA every 2 mo. for 6 yr. The cell aggregates became more synchronous and many typical embryogenic cells with dense cytoplasm were observed under a light microscope. The long-term embryogenic cells plated on MS basal medium still gave rise to numerous somatic embryos and converted into plantlets.