This paper studies whether team members’ past collaboration creates team-specific human capital and influences current team performance. Using administrative Medicare claims for two heart procedures, I find that shared work experience between the doctor who performs the procedure (“proceduralist”) and the doctors who provide care to the patient during the hospital stay for the procedure (“physicians”) reduces patient mortality rates. A one standard deviation increase in proceduralist-physician shared work experience leads to a 10–14 percent reduction in patient 30-day mortality. Patient medical resource use also declines with shared work experience, even as survival improves.