Case reports on 112,003 patients obtained through a prospective survey have been studied and submitted to computer processing. The significant findings have been reviewed and their importance discussed. The following points are noteworthy: the value of pretesting is doubtful; and routine pretesting is not a recommended procedure. The constant readiness of a fully equipped emergency tray offers far greater security and assurance of patient safety than the unpredictable and unreliable results of pretesting. The over-all incidence of nonfatal reactions is lower than has been previously indicated: 5.65 per cent for intravenous urography; and 2.33 per cent for intravascular studies. The incidence of fatal reaction (1 in 10,000) is higher than that reported on the basis of retrospective studies. This figure may or may not be duplicated in the next 100,000 examinations. The cause of death in some patients may be related to a combination of factors— primary disease, diagnostic procedure, and contrast medium. The over-all incidence of adverse reactions in patients with allergy is about twice that in the general population. The incidence of adverse reactions is highest in the third and fourth decades, and lowest at either end of the age spectrum. Incidence of reactions is equal in both sexes. History of reaction to previous examinations is not a contraindication to re-examination. The incidence is approximately 3 times that of the general population. Rapid injection rate, in intravenous urography, is accompanied by fewer reactions than a slow injection rate. A slow injection rate in intravenous cholangiography is accompanied by fewer reactions than a rapid injection rate. It is anticipated that this program will continue, so that additional meaningful data and significant information will be accumulated. The members of our Committee are of the firm belief that this program will become the foundation of a permanent national and international adverse reaction reporting system, thus meeting a great need. We invite the collaboration and support of all those interested and involved in the many phases of contrast medium work.