Current revisions of monographs for F-18 pharmaceuticals in the European Pharmacopoeia (Ph. Eur.) (Ph. Eur., 2011) call for a radionuclidic purity (RNP) of or better than 99.9%. However, the current method is not sufficient nor effective for testing this required RNP level. We present a theoretical model leading to a practical procedure for a simple test of RNP for F-18 compounds that tells whether or not the sample is pure with a statistical confidence of 97.5% (P=0.975). (C) 2011 Elsevier Ltd. All rights reserved.