Although school and education system leaders can mandate teachers' participation in professional development activities, various school-related, teacher-related and student-related factors influence the degree to which professional development opportunities ultimately result in the desired teaching and learning impacts. This study examined teachers' perceptions of the factors that influenced the impacts of a range of professional development activities in which they had participated. Constructivist grounded theory analysis of qualitative data provided by 131 teachers (reflecting 15 nationalities) led to the development of a new conceptual model for the trajectory from teacher professional development activities to student impacts. The model involved five stages: "intended" professional development, "received" professional development, "accepted" professional development, "applied" professional development and "student impacts." Various barriers influenced whether professional development was able to progress to each successive stage; the current data provided particular insight into the "structural" barriers that determined whether intended professional development was actually received by teachers and the "acceptance" barriers that determined whether received professional development was actually accepted by teachers. The new model extends existing frameworks by highlighting the importance of contextual influences on teacher professional development and providing further specificity regarding some of the gatekeeping factors that influence the outcomes of teacher professional development.