The purpose of the paper is to explore the way manufacturing firms use internal and external suppliers in the design and management of manufacturing networks. The main area of interest is to explore the similarities and differences between internal and external suppliers, with respect to their roles and the reasons for choosing a certaintype of supplier. We base our analysis on data from 104 Swedish manufacturing plants and their corresponding manufacturing networks of internal and external suppliers. The results of the study show that there are significant differences between the criteria that are influential in choosing a certain type of supplier. The choice of an internal supplier is largely based on a single corporate decision, while an external supplier has to perform well on a number of criteria (primarily quality, cost, and delivery dependability). When comparing the selection criteria withcompetitive priorities and plant performance, we find that the criteria for selecting external suppliers has a better match than those for selecting internal suppliers. The sample contained plants having only external suppliers as well as plants having both internal and external suppliers,but the selection criteria for external suppliers are the same for both groups and not dependent upon the presence or absence of internal suppliers.