This pedagogical review illustrates the differences between pharmacokinetic (PK) and pharmacodynamic (PD) measures, using insulin therapy as the primary example. The main conclusion is that PD parameters are of greater clinical significance for insulin therapy than PK parameters. The glucose-clamp technique, the optimal method for determining insulin PD, is explained so that the reader can understand the important studies in the literature. Key glucose-clamp studies that compare two basal insulin analogues - insulin glargine and insulin detemir - to Neutral Protamine Hagedorn insulin and to each other are then presented. The review further explains how PD parameters have been translated into useful clinical concepts and simple titration algorithms for everyday clinical practice. Finally, the necessity of overcoming patient and/or physician barriers to insulin therapy and providing continuing education and training is emphasised.