Although the volume/outcome relation for percutaneous transluminal coronary angioplasty (PTCA) is well established, it is unclear how the relation has changed over time. To examine trends in hospital and operator volume and outcomes for PTCA, we conducted a retrospective cohort study of discharge records of patients who underwent PTCA at nonfederal hospitals in Florida and New York from 1996 to 2001. Hospital/operator pairs were divided into 4 classes using American College of Cardiology/American Heart Association volume classifications. Outcome measurements were operator and hospital procedure volume and a combined end point of inpatient mortality and emergency coronary artery bypass graft surgery. Of 452,404 patients, the number of patients who underwent PTCA from 1996 to 2001 increased from 58,180 to 92,277, with a mean annual increase of 9.1%. The risk-adjusted end point of mortality and emergency coronary artery bypass grafting decreased over time, occurring in 2.8% of admissions in 1996 and in 1.6% of admissions in 2001. Class 1 hospital/operator pairs, which were operators performing >or=75 procedures at hospitals performing >400 procedures, had the lowest occurrence of the end point overall and in each year. The risk-adjusted end point difference between classes narrowed over time. In conclusion, outcomes were best for patients receiving care from class 1 hospital/operator pairs, and an increasing proportion of patients received care from class 1 pairs. There were outcome differences within subpopulations of operators in classes 2 and 4, which suggest possibilities for alternative volume classification guidelines.