Reform-minded science educators have expended significant effort developing and testing high quality curricular materials and techniques with the expectation that science instructors will recognize the superiority of these materials and adopt them. Adoption is assumed to be a relatively unproblematic process and the expectation is that the number of instructors using these materials will naturally expand, eventually leading to a critical mass of instructors teaching in a fundamentally new way. Unfortunately, current and historical evidence does not indicate promise for this approach to reform. This workshop presentation gives some of the reasons why educational reform is so slow and difficult. It also identities shortcomings of standard approaches to reform and explores alternative models that may be fruitful in overcoming these weaknesses.