In this thesis, we consider a problem of determining part input sequences in flexible manufacturing systems (FMSs) with the objective of minimizing makespan. It is assumed that FMSs are partially pooled and part selection and loading plans are given. Three heuristic methods are developed for this problem. The suggested methods dynamically determine a set of parts, called the part input group, to be released and production ratios of the parts. To evaluate suggested methods, computational experiments are carried on randomly generated test problems. Performance of the methods are compared with an existing method in which minimal part set (MPS) is used. Results of simulation experiments show that some of the suggested methods outperform the existing method.