To determine if high-dose gadolinium chelates are less nephrotoxic than iodinated contrast. Records of 342 patients who had received high-dose gadolinium (.2 to .4 mmol/kg) for magnetic resonance imaging were reviewed to identify patients who had also received iodinated contrast for radiographic examinations. Their clinical course and laboratory data were reviewed to identify changes in serum creatinine attributable to the contrast agents. In 64 patients, serum creatinine data were available pre and post both gadolinium and iodinated contrast. The mean change in serum creatinine after gadolinium in these 64 patients was -.07 mg/dL (-6 mumol/L). By comparison, the mean change in serum creatinine in the same patients after iodinated contrast was .35 mg/dL (+31 mumol/L) from 2.0 +/- 1.4 to 2.3 +/- 1.8 (P = .002). Eleven of the 64 patients had iodinated contrast-induced renal failure (.5 mg/dL or greater rise in serum creatinine); none had gadolinium contrast-induced renal failure despite the high gadolinium dose and high prevalence of underlying renal insufficiency. High-dose gadolinium chelates are significantly less nephrotoxic than iodinated contrast.