It's known that in Brazil, the main factors that influence the alkaloids formation in Burley tobacco are: quantity of rain during the crop; nitrogen dosages and sources; topping heights and harvesting time. Recent studies have shown that the interaction between cultivar and climate are very important factors for the alkaloids formation. Rainy crops produce tobaccos with lower alkaloids, and less rains during the crop, provide the production of tobaccos with higher alkaloid levels. The objective of this study was to evaluate the importance of the cultivars and climate in the alkaloids formation in the burley tobacco. This study was done with four experiments in different areas in the west of Santa Catarina state, Brazil, in the 2002 crop (two experiments) that was a less rainy one and 2003 (two experiments) that was a rainy one. The design of the experiments was randomized blocks with three replications, with 48 plants/plot (four rows with 12 plants each). The treatments had been constituted by different cultivars: a) TN 90; b) NC 3; c) HB 04P; d) DBH 9951; e) DBH 2051; f) DBH 2052; g) DBH 2053 h) DBH 2152; and i) DBH 2153. Dosages of nutrients used in the 2002 crop and 2003 was 200 and 260 kg/ha of nitrogen, 117 and 117 kg/ha of the phosphorus, and 270 and 300 kg/ha of the potassium, respectively. The total precipitation during the months of August to January in the 2002 crop was 861 mm, with average of 144 mm/month. For the 2003 crop, in the same period, the total precipitation was 1.587 mm with average of 265 mm/month. The results had shown that climate (rains) in the developing phase of the culture, is the factor that causes the strongest influence in alkaloids formation and the cultivars are in the second position. Rainy crop = above average rainfallLess rainy crop = below average rainfall