System designers and technology strategists have long recognized the concept of an architectural control point as a way to identify parts of a system that have particular strategic importance. Despite the vast body of work on system architecture in the engineering design literature, however, few authors have attempted to define architectural control points or study them systematically. Moreover, some industry participants have questioned whether architectural control is still a valuable or achievable goal in an era of increasingly open standards. This paper offers tentative definitions of architectural control, architectural control points, and architectural strategy. In a longer version of the paper, the utility of these concepts is demonstrated through examples drawn from the history of the personal computer industry. These examples reveal both simple and subtle interactions between system design and market competition, and suggest that architectural strategy continues to play an important role in the competitive dynamics of system-oriented industries.