To date most separation synthesis work has been directed towards the sharp separation, pure component product problem. However, there exist separation processes, particularly in the petroleum industry, which are concerned with the manufacture of multicomponent products. Many of these are effect products, i.e. products whose specifications are in the form of a property such as density or vapour pressure and therefore are satisfied by a region of compositions. Such products present opportunities for the use of non-sharp separations and; stream splitting and blending, yet no systematic synthesis method which exploits these has been developed. An automatic procedure for the solution of multicomponent product synthesis problems is presented which does not require an explicit superstructure. Separator functions are not predetermined and systematic stream splitting and blending are included. The synthesis algorithm employs a depth first tree search in order to locate solutions and unit design variable discretisation to reduce the search space. The algorithm generates a set of good, feasible solutions which may be further optimised by continuous means.