Recently cyclosporin A (CsA) capsules have been introduced to meet a number of disadvantages associated with the use of the oral solution. We compared the pharmacokinetics of the oral solution and the capsules in a group of nine renal transplant patients during the first 3 weeks after transplantation. After a morning dose of CsA, whole blood concentrations were measured at regular intervals for 12 h. Subsequently, a cross-over was made to the alternative form of administration, and 3 or 4 days later a second pharmacokinetic profile was obtained. Comparison of the trough level, the maximum concentration, the time to reach the maximal concentration and the area under the blood concentration curve, showed no significant differences. Our findings thus suggest a similar bioavailability of CsA administered as oral solution or in capsules in the early post-transplant period.