Subcellular fractionation techniques have added a new dimension to studies of synaptic function. Much of the research of the past decade has been devoted to improving techniques — for subcellular fractionation techniques are full of pitfalls if applied uncritically and there are many problems concerned with the homogeneity and purity of the fractions. In the next few years rapid progress can be expected in our understanding of the molecular mechanisms involved in transmitter storage and release and the way in which drugs and toxins interfere with these mechanisms. Combined electrophysiological, morphological and biochemical studies of the type now being carried out on theTorpedo will be particularly useful in such research.