Research on modularity and commonality has grown substantially over the past 15 years.Searching 36 journals over more than the past 35 years, I identify over 160 references in the engineering and management literature that focus on modularity or commonality in the product and process development context. Each of the references is analyzed along the dimensions subject, effect, and research method. The subjects of these studies have been products, processes, organizations, and even innovations, although the set of references shows a strong preference towards products. Similarly, a broad range of effects has been studied, albeit with the topic cost dominating all other effects. A variety of research methods has been applied to the study of modularity and commonality but the distribution of research methods differs substantially for modularity and commonality research. Despite the wealth of existing research, there are still significant opportunities for future research. In particular, studies that incorporate modularity and commonality's multiple effects on various players along the supply chain, that combine multiple research methods, and that follow systems over time appear very promising.