Starch, free sugars and protein contents, and the specific activities of enzymes of starch metabolism were determined in tobacco callus cultured under shoot-forming and non-shoot-forming conditions. Shoot-forming cultures contained higher levels of starch, free sugars and protein. Shoot-forming cultures had higher specific activities for starch-synthesising enzymes throughout culture. On the other hand, higher levels of activity for starch-degrading enzymes in shoot-forming tissues were only observed during organized development. The role of phosphorylase in the cultured tissue was not clear.