Abstract: Methods and compositions are provided for preparing stabilized interferons and for combining stabilized interferon with cigarettes. Special domains of the interferon molecule are recognized by methods which are described. A means for constructing these domains by recombinant DNA technology is detailed. A method for stabilizing natural interferons is also described. A process for combining the stabilized interferon with cigarettes is presented.The combination of interferons and cigarettes is synergistic, especially because interferon effects are magnified at elevated temperatures and because interferon has a preferential effect on tumor cells, but for other reasons as well. The process is not obvious and will be beneficial to a large segment of mankind; those who use tobacco products.