More than twenty pyridine alkaloids have been identified in tobacco leaves. Some of them having both pyridine and pyrrolidine rings in their molecules may be considered as the derivatives of nornicotine (3-(2•L-pyrrolidyl) pyridine). In spite of a number of N•L-acyl and N•L-carboalkoxy derivatives of nornicotine having been reported, no N•L-alkyl derivatives other than nicotine have been isolated as the tobacco alkaloids. During our studies on basic compounds of air-cured tobacco, a new minor alkaloid was found in one of the fractions of aged burley tobacco, identified as N•L-isopropylnornicotine (I) via alumina column fractionation, GC-MS analysis using a glass capillary column, and comparison with N•L-isopropylnornicotine prepared by the reaction of nornicotine with isopropyl bromide. Mass spectrometric data (including fragment peaks suggesting a pyridine ring, pyrrolidine ring, nornicotine moiety, and isopropyl group) and retention time in gas chromatography confirmed the structure. This is the first case that a N•L-alkyl pyridine alkaloid except for N•L-methyl derivatives was identified in tobacco leaves.