Six kinds of sugars (Maltose, Sucrose, Glucose, Fructose, Mannose and Lactose) and four kinds of organic acids (Malic, Tartaric, Lactic and Citric) were added by 2-10% for the former and 0.2-1.8% for the later in quantitatively to the inferior quality of Flue-cured leaf tobaccos, and treated at 135$^{circ}C$ for 10 minutes to examine the effect on deliveries of tar and nicotine in smoke, variation of smoke pH and smoking taste. The results obtained are as follows. Tar and nicotine deliveries in smoke of tobacco show a great reduction with 5-6% addition of sugars. Reduction of nicotine delivery was to be 19% with addition of Glucose. Tar in smoke was, however, increased by 5-8% with 4% addition of Sucrose or Lactose. On the other hand, 4% addition of Glucose and Fructose gave 1 % reduction of tar delivery, but the reduction rate became to be small with increase of adding quantity. The smoking taste by the addition of Glucose and Fructose tobacco was found to be milder than by the other sugars. Tar and nicotine deliveries show a decreasing trend with the addition of organic acid, and Tartaric acid, among the organic acids described above, had greater effect than the other acids. 1% addition of Tartaric acid gaves 10-11% reduction in tar and nicotine delivery, and a fall of smoke pH, from 6.40 to 6.05, was found. Smoking taste by the addition of Lactic and Tartaric acid had milder than the others. And heat treatment for 10 minutes at $135^{circ}C$ gave also better on smoking taste. The addition of mixture of sugars and organic acids, (Glucose 4%+Lactic acid 0.8% + Tartaric acid 0.2%) and then the successive heat treatment for 10 minutes at $135^{circ}C$ improved greatly the quality of Fluecured leaf tobacco, and nicotine were reduced to 16-29%, and pH was changed from 6.46 to 6.14.