Reaction path synthesis, the generation of a network of alternative reaction routes for the manufacture of a desired product and the selection of an optimal route, represents a key step in arriving at environmentally sound process designs. In this paper a systematic procedure for organic reaction path synthesis is described in which minimum environmental impact considerations are incorporated in order to exploit the earliest opportunities for waste reduction. The size of the reaction path synthesis problem is reduced by decomposing it into a series of steps, each of which is approached in a guided way. This is achieved by first introducing a group based computer aided raw material and stoichiometric co-product design step. With the raw materials, stoichiometric co-products and product known, the reaction path synthesis problem is no longer open ended. Feasible stoichiometries between these materials are determined and promising candidates are identified according to the Methodology for Environmental Impact Minimization (Pistikopoulos et al., 1994).