This study examines the use of career ladders for medical assistants (MAs) in primary care practices as a mechanism for increasing wages and career opportunity for MAs. A growing body of research on primary care suggests that successful expansion of support staff roles such as MAs may have positive organizational and quality of care outcomes, but little is known about worker outcomes. Evaluate the effectiveness of career ladders in improving wages and career opportunity among MAs. We use a mixed-methods design to evaluate the impact of career ladders on MA job quality. We draw on interview data collected from 115 key informants at four large health systems (ranging from 24 to 29 clinics each), and we analyze wage and employment data for MAs from primary care clinics in the four health systems in the sample. We describe the MA career ladder context and infrastructure within primary care clinics and evaluate the rewards to MAs for participation in the career ladder programs. The expanded roles within career ladders for MAs focused on the following four clinical and educational areas: panel management and care coordination, EHR documentation support, supporting delivery of person-centered care, and supervision and training. The three primary components of the career ladder infrastructure were training and education for MAs and providers, credentialing and certification for MAs, and differentiated job levels for MAs. The use of career ladders in the four large health systems in our case study sample resulted in yearly income increases ranging from $3000 to $10,000 annually. Investing in career ladders in primary care clinics can improve MA job quality while also potentially addressing issues of equity, efficiency, and quality in the health care sector.