A hybrid manufacturing system (HMS) is a manufacturing system where flexible manufacturing system (FMS) and conventional manufacturing system (CMS) exist simultaneously. This study investigated the combined part selection (PS), load sharing (LS) and machine loading (ML) problem in HMS to obtain consistent solutions to the related decisions by concurrently considering the three and to improve the overall system performance by coordinately utilizing the production resources of FMS and CMS. This problem is formulated as a mixed integer programming model. A special case of the problem consisting of only LS and ML is also discussed and modelled. The applications of the models are demonstrated by example problems. Solution procedures based on Lagrangian relaxation are also suggested for larger-sized problems