The absolute bioavailability of HB 420 (a new pharmaceutical form of glibenclamide) was investigated in comparison with an i.v. infusion of glibenclamide and also in comparison with HB 419 (Semi-Euglucon) on a group of 10 healthy volunteers with the aid of a highly specific bioanalytical detection method. A comparison of the dose-corrected areas under the concentration-time curves yielded an absolute bioavailability of 102% for HB 420. The relative bioavailability of HB 419 to HB 420 was 73%. This resulted in a bioequivalent dosage relationship of 2.5 mg HB 419 to 1.75 mg HB 420. It could be experimentally confirmed on further 10 healthy volunteers that 1.75 mg HB 420 (identical with Semi-Euglucon N) and Semi-Euglucon (containing 2.5 mg HB 419) are bioequivalent with respect to the absorbed quantity of active agents. The differences in absorption rate between the new and the old form did not lead to relevant differences in the glucose profile and the release of insulin, so that the two forms can be regarded as being pharmacodynamically equivalent. The median for the terminal elimination half-life for glibenclamide was 1.38 hours (min. 0.65, max. 4.64 hours), the total clearance was 100 ml/min and the steady-state distribution volume was 7.3 l (0.1 l/kg). On the basis of half-life, it can be expected that the elimination of the unchanged substance will be virtually complete within 10-12 hours. During long-term therapy, however, it cannot be ruled out that in some diabetics cumulation could occur, the cause of which cannot be explained by the data presented.