BACKGROUND: Adverse reactions to radio-contrast media (CM) represent a serious problem. There have been few reports about incidence of adverse reactions to CM in general population. OBJECTIVE: The purpose of this study was to evaluate the incidence and clinical features of adverse reactions to low osmolar, nonionic contrast media in the general population. METHOD: A total of 12,177 examinee underwent contrast-enhanced CT using low osmolar, nonionic CM. Immediate adverse reaction is defined as symptoms occur within 1 hour after contrast administration and late adverse reaction is defined as symptoms occur more than 1 hour but less than 7 days following contrast administration. A questio-nnaire was used to collect general and medical information. RESULT: Adverse events were noted in 306 cases of total 13,552 cases. The incidence of adverse reactions was 2.3% and severe reactions was 0.04%. The incidence of immediate reaction was 2.0% and late reactions was 0.3%. Symptoms of immediate and late reactions were nausea/vomiting (22.2%), erythema/pruritus/urticaria (74.2%), angioedema (2.0%) and hypotension (1.6%). CONCLUSION: The incidence of adverse reaction to low osmolar, nonionic CM was 2.3% in the general population. The skin was the most commonly affected site of adverse reactions.