Gadopentetate dimeglumine is an intravenous contrast medium used in magnetic resonance imaging. To determine its safety, the authors summarized data concerning adverse reactions, laboratory parameters, and other assessments for 1,068 adult patients who received gadopentetate dimeglumine in United States clinical trials. For all studies, 213 of 1,068 patients (19.9%) who received gadopentetate dimeglumine experienced one or more clinical adverse reactions. Most of these reactions were minor and short-lived. Hematologic, blood chemistry, and urinary evaluations showed no apparent drug-related effects, with the exception of a transient, asymptomatic rise in serum iron and bilirubin levels in some patients. Other safety assessments--electrocardiography, electroencephalography, neurologic examinations, and vital signs--showed no clinically significant trends in change from baseline results. It was concluded that gadopentetate dimeglumine demonstrated a high degree of safety and tolerance.