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As suggested by several past studies (Barkan and Hinckley, 1993; Eking, 1988; Gebala, 1992; Beiter et al., 2000; Shibata et al., 2001), complexity in the assembly process has a strong correlation with the occurrence of defects. The authors propose a new method that uses a product’s complexity to predict defect rate (Shibata et al., 2001 and 2003). This method provides metrics for assembly complexity using two engineering measures: 1) assembly time estimates and 2) ease-of-assembly ratings. Extensive field data for consumer audio equipment assembled at various manufacturing sites around the world provide the means to validate the proposed metrics. A new process-based complexity factor uses a “time standard” defined for a set of assembly tasks. Predicted defect rates, based on this process complexity, exhibit a significant correlation with actual defect data. Another factor, the design-based complexity factor, uses the “Design for Assembly” method for evaluating an assembly and allows the user to predict defect sources not captured by the process-based complexity factor. Combining these complexity factors not only improves prediction accuracy but also provides guidelines for improving the original design concept as well as each process step. The authors conclude with an example of implementing the Assembly Quality Methodology using the new complexity factors for globally distributed manufacturing.