It is common practice to dispense radiopharmaceuticals into empty sterile vials for dispatch to the departments where they are to be administered. It has been noted that on withdrawal of technetium-99m dimercaptosuccinic acid injections (99Tcm-DMSA) which have been dispensed into such vials, the activities obtained are lower than expected. To explain this phenomenon, the adsorption of 99Tcm-DMSA onto commercially available, empty, sterile vials has been investigated. The 99Tcm-DMSA solutions were prepared using kits from two manufacturers and were tested in vials from two manufacturers and the original kit vials. Adsorption of 99Tcm in one DMSA/vial combination after storage for 4 h was 49.6% (+/- 4.5% S.E.M.), but typically, adsorption was approximately 12% after 4 h. Although rate of adsorption was found to vary with storage conditions, no conditions satisfactorily overcame the effect. In vials from one manufacturer, the 99Tcm adsorption was predominantly on the glass, while in vials from the other, it was predominantly on the rubber stopper. It is concluded that the compatibility between vials and radiopharmaceuticals must be investigated in the hospital radiopharmacy.