Alkane composition was determined on the leaves of 52 Nicotiana species and 2 horticultural species. All Nicotiana spcies except N. glauca contained substantial amounts of branched (iso- and anteiso-) alkanes. Nieotiana species were divided roughly into six groups by their resemblance on alkane composition.This classification system was correlated to the botanical classification.The evolution of Nicotiana species was discussed on the basis of alkane composition.