Abstract: A useful algorithm which may be used in selecting the optimal combination of solvent systems forpaper and thin layer chromatography assisted by computer was presented. Depending upon the number of solvent systems and drugs to be tested, two kinds of methods, "stepwise combination" and "combination by good choice", were provided. Computation of 26 food dyes and 22 sulfa drugs was made by TRS-80 μ-computer with satisfactory results.Using these methods, some shortcomings originated from the numerical taxonomic technique with information content as selection criterion and from the taxonomic technique of information content of system-difference were overcome, and various combination programs could be given as well. The proposed method can also be used by manual calculation without any computer.