Plants from 64 Nicotiana species were sampled in the greenhouse in 1983 and 1984 and from the field in 1985 and 1986 for the purpose of developing a chemical profile of each species. Mature green leaves were harvested at flowering, freeze-dried and ground to pass a 1 mm screen prior to chemical analysis. In this study we report the type and amounts of nicotinoid alkaloids. Alkaloid values were determined by glass-capillary gas chromatography and were averaged over the two years for each environment. Both total alkaloids (mg g-1 dry weight) and the distribution (percentage composition) of nicotine, nornicotine, anabasine, and anatabine were highly correlated between years for greenhouse and field samples. Greenhouse and field data were highly correlated, although total-alkaloid levels were significantly higher from field-grown plants. All of the Nicotiana species tested contained a measurable alkaloid fraction (at least 10 µg g-1). There was a wide range in total-alkaloid levels with nearly a 200-fold difference among greenhouse-grown samples and a 400-fold difference among field-grown species. In general, total-alkaloid levels among the species were found to be relatively low. Eleven species were found to have a different alkaloid composition when green leaf and air-dried samples were compared. Evidence is presented for the association between alkaloid characteristics and the phylogenetic classification of the species in the genus.