This report describes a protocol for the regeneration of fertile plants from mesophyll protoplasts of Arabidopsis thaliana race Columbia (C24). Regeneration was rapid and reproducible. The protocol is especially novel in that a large proportion of regenerating protoplasts regenerated via direct somatic embryogenesis. Protoplasts isolated from in vitro-grown plants entered sustained division after 3–5 d in culture medium and over a period of several days 6–22% of protoplasts underwent at least one cell division. Approximately 2–16% of these protoplasts continued to divide and after 3 weeks in culture had formed macroscopic colonies, of which 70–80% were regular embryo-like structures. Four weeksafter release from the alginate culture matrix and transfer to solid medium in the light, 68–88% of these structures had produced well-developed shoots. Shoots could be maintained in culture or established in peat blocks. The regenerated plants were fertile.