This article presents a framework for characterizing architecturally significant requirements (ASRs) on the basis of an empirical study using grounded theory. The study involved interviews with 90 practitioners with an accumulated 1,448 years of software development experiences in more than 500 organizations of various sizes and domains. These findings could provide researchers with a framework for discussing and conducting further research on ASRs and can inform researchers' development of technologies for dealing with ASRs. The findings also enrich understanding of requirements and architecture interactions, allowing the twin peaks to move from aspiration to reality.