Until recently, practical diets fed to cattle were assumed to provide sufficient chromium to meet requirements. Recent research now suggests that in some situations practical diets may not contain adequate chromium to maximize certain biological processes in ruminants. Supplementation of chromium has increased blood glucose clearance rates following intravenous infusions of glucose and/or insulin in some studies with calves. However, one experiment with lactating cows indicated that supplemental chromium decreased sensitivity to insulin. Differences in responses may reflect the energy balance of the animal. Early in lactation, cows are in a negative energy balance, whereas growing calves are in a positive energy balance. Supplemental chromium has increased milk production in first lactation cows. Gain and feed efficiency have been increased by supplementation of chromium in some experiments, but not in others. Lipid metabolism also has been affected by supplemental chromium. Lower concentrations of blood ketone bodies have been observed in cows supplemented with chromium. Chromium supplementation has not altered backfat thickness or increased lean composition of beef carcasses. Several forms of supplemental chromium have been investigated in cattle diets, including chromium nicotinic acid complex, chromium tripicolinate, high chromium yeast, amino acid-chelated chromium, and chromium chloride. Responses have varied between sources in the few studies where different supplemental sources have been compared. Presently, no supplemental chromium sources are approved for addition to cattle diets. One problem is that little is known regarding the bioavailability of chromium in feeds commonly used in cattle diets. Further research is needed to determine when supplementation of chromium will impact cattle performance. J. Trace Elem. Exp. Med. 12:141–147, 1999. © 1999 Wiley-Liss, Inc.