Purpose: To determine the incidence and risk factors of immediate hypersensitivity reactions to gadolinium-based magnetic resonance (MR) contrast agents. Materials and Methods: Institutional review board approval and a waiver of informed consent were obtained. A retrospective study of patients who had been given gadolinium-based MR contrast media between August 2004 and July 2010 was performed by reviewing their electronic medical records. In addition to data on immediate hypersensitivity reaction, the kinds of MR contrast media and demographic data including age, sex, and comorbidity were collected. To compare the groups, the χ 2 test, Fisher exact test, χ 2 test for trend, Student t test, analysis of variance test, and multiple logistic regression test were performed. Results: A total of 112 immediate hypersensitivity reactions (0.079% of 141 623 total doses) were identified in 102 patients (0.121% of 84 367 total patients). Among the six evaluated MR contrast media, gadodiamide had the lowest rate (0.013%) of immediate hypersensitivity reactions, while gadobenate dimeglumine had the highest rate (0.22%). The rate for immediate hypersensitivity reactions was significantly higher in female patients (odds ratio = 1.687; 95% confidence interval: 1.143, 2.491) and in patients with allergies and asthma (odds ratio = 2.829; 95% confidence interval: 1.427, 5.610). Patients with a previous history of immediate hypersensitivity reactions had a higher rate of recurrence after reexposure to MR contrast media (30%) compared with the incidence rate in total patients (P < .0001). The incidence of immediate hypersensitivity reactions increased depending on the number of times patients were exposed to MR contrast media (P for trend = .036). The most common symptom was urticaria (91.1%), and anaphylaxis occurred in 11 cases (9.8%). The mortality rate was 0.0007% because of one fatality. Conclusion: The incidence of immediate hypersensitivity reactions to MR contrast media was 0.079%, and the recurrence rate of hypersensitivity reactions was 30% in patients with previous reactions.