Drug flow models attempt to estimate the availability of illicit drugs at various points: source countries, transit countries, and consuming countries. A sequential transition and reduction method is utilized. The model transitions availability at one stage to the next through conversions or reductions based on data from multiple sources. The model for the flow of heroin through Ukraine begins with unfinished poppy leaving Southwest Asia along three major exit corridors: (1) overland westward through Iran to Turkey; (2) north through Central Asia, then westward directly to Eastern Europe or Turkey and (3) south through Pakistan and westward by sea craft to United Arab Emirates for subsequent transport to Africa, the United States, and Europe. There are indications that between 70 to 80 percent of Southwest Asian heroin bound for Europe are transported overland via truck or rail car through Turkey, then north along the Balkan transit route. The Balkan route has expanded to include a northern and southern spur. Heroin shipped along the northern spur transits Ukraine and other northeastern European regions. With increased production of heroin in Afghanistan continuing and Iran continuing to crack down on smuggling, the potential for even more heroin transiting through Ukraine continues. Ukraine has become a significant conduit for Southwest Asian heroin bound for European markets. Ukraine has become a legitimate opiate producer in its own right, cultivating approximately 3000 new hectares of illicit poppy fields annually. After a brief discussion on the production, producing regions, and trafficking routes of heroin, this paper summarizes a preliminary heroin flow model through Ukraine.