Systematic tests resulted in a nutrient solution containing the following, in milligrams per liter, for the culture of protoplasts isolated from Nicotiana tabacum L. callus cells: Murashige and Skoog salts (T. Murashige and F. Skoog, 1962. Physiol. Plant. 15: 473-497); sucrose, 15,000; mannitol, 110,000; alpha-naphthaleneacetic acid, 0.6; kinetin, 0-0.1; thiamine.HCl, 10; pyridoxine.HCl, 10; nicotinic acid, 5; myo-inositol, 100; and glycine, 2. In this medium, regeneration of cell wall has been observed in 85% and resumption of cell division among 35% of the protoplast isolates.