D-Pantethine is a compound in which two molecules of D-pantetheine bind through an S-S linkage. D-Pantethine is available from commercial sources as well as from D-pantothenic acid. We investigated if D-pantethine has the same vitamin activity as D-pantothenic acid by comparing the recovery from a deficiency of D-pantothenic acid in rats. D-Pantothenic acid-deficient rats were developed by weaning rats on a diet lacking D-pantothenic acid for 47 d. At that time, the urinary excretion of D-pantothenic acid was almost zero, and the body weight extremely low, compared with the control (p<0.05); the contents of free D-pantothenic acid were also significantly reduced in comparison with those of controls (p<0.05). D-Pantothenic acid-deficient rats were administered a diet containing D-pantothenic acid or D-pantethine for 7 d. D-Pantethine and D-pantothenic acid contents of the diets were equimolar in forms of D-pantothenic acid. We compared various parameters concerning nutritional status between rats fed D-pantothenic acid- and D-pantethine-containing diets. The recoveries of body weight, tissue weights, and tissue concentrations of free D-pantothenic acid, dephospho-CoA, CoA, and acetyl-CoA were identical between rats fed diets containing D-pantothenic acid and D-pantethine. Thus, the biological efficiency for recovering from a deficiency of D-pantothenic acid in rats was equivalent between D-pantothenic acid and D-pantethine.