This paper reports the results of a comprehensive review and analysis of the assembly line balancing literature. Quantitative developments and qualitative issues are addressed at both the strategic and tactical levels. The numerous quantitative and qualitative factors which the literature mentions could impact the design, balancing and scheduling of assembly systems are organized into an eight-level hierarchical, factor/decision taxomony. This comprehensive taxonomy is used to assess our progress in assembly system design and operation. Finally, from the results of the literature review and progress assessment, suggestions for future research on socio-technical assembly systems are offered.