LOCAs offer significant advantages in certain situations, but in others their advantages are either absent or unproved. On the basis of current knowledge and practice, there is no legal mandate to use these agents. Clear advantages to the use of LOCAs are (a) decreased pain and discomfort in painful examinations (in this regard, however, they are equivalent to dilute HOCAs in intraarterial digital subtraction angiography), (b) decreased myocardial and generalized hemodynamic effects, and (c) decreased osmotic load, perhaps important in infants or severely dehydrated patients. LOCAs may be helpful in examinations of patients with alteration of the blood-brain barrier (major trauma, tumor, or stroke), prior contrast media reactions, and marked anxiety. However, in the following areas, there are, as yet, no clear answers about the use of LOCAs: (a) reduction of overall mortality, (b) reduction of morbidity in elderly patients, and (c) reduction of the risk of nephrotoxicity in patients either with or without specific risk factors such as diabetes mellitus or renal failure.