In the design of distillation processes, it is frequently necessary to obtain a specified purity of certain product from a given feed mixture by the use of an existing column. The only variable within the designer's control is the reflux ratio. This design problem cannot be solved easily by existing computational methods. In general a trial-and-error approach is used. To avoid this difficulty, this problem is solved as an estimation problem by the use of the quasilinerization approach. To show the effectiveness of this approach, several problems are solved. In general, a four-digit accuracy is obtained in four iterations with very approximate initial approximations. Furthermore, this approach can treat the overdetermined system in a straightforward manner by the use of least squares criterion and minimization. Only the cases with constant total flow rates of the vapor and liquid streams within each section of the column are considered. The relative volatilities are also taken to be constant throughoutthe column.