Total solanesol was quantitatively determined in tobaccos of different types and origins (American tobaccos : flue-cured, burley and Kentucky, Greek and Turkish oriental, Columbian and French dark air-cured, French flue-cured). French tobaccos showed a low content in solanesol compared with the others. Experiments in staggered harvesting (P.B. variety) involving topped and non-topped plants have shown that total solanesol generally decreased with topping but strongly increased between the 60th and 80th day of growth, and then increased less rapidly until the 100th day. Contents increased from lower leaves to the upper. Quantitative determination of total solanesol made on tobaccos subjected to nitrogen fertilization experiments showed that solanesol decreased with N supplies ranging from 60 to 480 kg/ha. (Nitrogen. )