Changes were investigated in trace alkaloid composition of MC-1(bright) and Burley-21 (burley) leaf lamina during curing. Seventeen alkaloids were identified. The total level of trace alkaloids decreased by approximately 60% in both MC-1 (flue-cured) and Burley-21 (air-cured). Although the level of most alkaloids also decreased, 2,3'-bipyridyl and four nornicotine derivatives, i.e. N'-hexanoyl-, N'-octanoyl-, r-(6-hydroxyoctanoyl)- and r-(7-hydroxyoctanoyl)-nornicotine, increased during curing in both varieties. Differences in the trace alkaloid composition of cured leaf lamina among MC-1 (bright), Burley-21 (burley) and Basma (Orient) were also studied. In all varieties, N'-formylnornicotine, nicotyrine, anabasine and cotinine were present at high concentrations relative to the other trace alkaloids. The alkaloids which were present in a relatively high concentration in particular varieties, were as follows: MC-1; N'-formylanabasine, Burley-21; N'-hexanoyl- and N'-octanoyl-nornicotine, and Basma; cotinine and N'-formylanatabine.