Reduced nitrogen fertilization is a major characteristic of Virginia tobacco culture. Compared to wheat and maize fertilization, the difference is considerable. As tobacco is grown on 6000 ha in Northern Croatia, it can be assumed that soil and water pollution by nitrates is substantially reduced on this areas. Pedoclimatic conditions, lighter soils and lower precipitation intensity influenced higher surface, runoff, as well as translocation of water into lower soil horizons and leaching of nitrates, caused by low absorption. Since mainly small farms have been found in this region certain problems occurred in tobacco production due to its frequent growing in a very narrow crop rotation or even in monoculture. Negative effects of such growing include spreading of diseases and pests, partial exhaustion of nutrients and reduction of tobacco yield and quality. These investigations will have a long-term character and are carried out on the experimental field of the Tobacco Institute Zagreb. Several types of crop rotation were tested: tobacco monoculture, two-crop (winter wheat, tobacco), three-crop (winter wheat, tobacco, maize), four-crop (winter wheat, tobacco, maize, soybean), five-crop (maize, soybean, winter wheat, oil-seed rape and tobacco) and six-crop (red clover, red clover, maize, soybean, wheat, tobacco) rotation. Tobacco is the key crop in these investigations while winter wheat and oil-seed rape were the preceding crops in trials. Investigations started in 1987 and were carried out on semigley soil (sandy loam) characteristics of the area where flue-cured tobacco is grown in Northern Croatia. The soil is of poor porosity in the eluvial (E/Bt) and illuvial (Bt) horizons. Tobacco growing in monoculture reduced the yield from 2.63 t/ha in the first year (1987) to 1.56 t/ha in the eighteenth year (2005). A significantly lower yield and quality were obtained after the fourth year of tobacco monoculture compared to tobacco growing in crop rotation. Tobacco grown in crop rotation had a higher percent of a better quality. The highest nitrate content in plough and sub-plough layers was recorded at lysimeter where the crop rotation involved maize and wheat, which was succeeded by tobacco. The lowest nitrate content (8.7 kg NO_3-N/ha) was leached in unfertilized tobacco monoculture, which served as check treatment. The highest content of leached nitrogen (46.3 kg/ha NO_3-N) was recorded after the harvest of maize, which was fertilized with 180 kg nitrogen, wheat fertilized with 160 kg of nitrogen, was shown. More intensive agricultural practices (deeper ploughing, subsoiling, frequent cultivation) will enable a more rapid percolation of water through the soil profile as well as leaching of larger nitrogen quantities.