Cultures of normal tobacco callus tissue 3 weeks after subculture contain free and bound forms of cinnamic, caffeic, and ferulic acids and bergapten, and bound umbelliferone, esculetin, and scopoletin. Cultures of tobacco crown gall tumor tissue lack cinnamic acid, umbelliferone, and bergapten; but they contain free as well as bound esculetin and scopoletin, and higher total levels of each of these coumarins than normal tissue. It is suggested that biosynthesis of coumarins in tumor cells has been diverted from the umbelliferone–furanocoumarin pathway in favor of esculetin and scopoletin.