The absence of a universally accepted definition of radiocontrast nephropathy (RCN) has hampered efforts to characterize effectively the incidence and the clinical significance of this condition. The objective of this study was to identify a clinically relevant definition of RCN by assessment of the relationships between increases in serum creatinine (Scr) of varying magnitude after coronary angiography and clinical outcomes. An electronic medical database was used to identify all patients who underwent coronary angiography at the University of Pittsburgh Medical Center during a 12-yr period and abstract Scr levels before and after angiography, as well as demographic characteristics and comorbid conditions. Changes in Scr after angiography were categorized into mutually exclusive categories on the basis of absolute and relative changes from baseline levels, with a separate category denoting "unknown" change. Discrete proportional odds models were used to examine the association between increases in Scr and 30-d in-hospital mortality and length of stay. A total of 27,608 patients who underwent coronary angiography were evaluated. Small absolute (0.25 to 0.5 mg/dl) and relative (25 to 50%) increases in Scr were associated with risk-adjusted odds ratios for in-hospital mortality of 1.83 and 1.39, respectively. Larger increases in Scr generally were associated with greater risks for these clinical outcomes. Small increases in Scr after the administration of intravascular radiocontrast are associated with adverse patient outcomes. This observation will help guide the post-procedure care of patients who undergo coronary angiography and has important implications for future studies that investigate RCN.