Processes of a real world manufacturer involve a nurnber of batch-processing operations. Generally, these operations require the decision on batch sizes of products and there is no specific rule to set batch sizes of all products simultaneously so that the sum of the weighted expected cycle times of ali products is minimized. The weights represent different levels of importance for products. In this study, we proposed an efficient genetic algorithm to determine the batch size combination that minimizes this sum. The proposed GA was tested on three different data sets, having number of products ranging trom 7 to 12. The results show that , for sorne cases,the proposed GA 1s etfect1ve in locating the global optimum solutions.