There has been considerable controversy regarding the optimum route of administration of drugs during cardiopulmonary resuscitation (CPR). Much of the confusion has arisen because the results of investigations in animals have been extrapolated to CPR in man. This may be inappropriate for a number of reasons. Experimental cardiac arrest in a previously healthy animal may not reproduce accurately the patterns of absorption or distribution of drugs given to man, particularly after non-parenteral administration. The effect of drugs on restoration of normal rhythm may be very different in the experimental animal in comparison to the diseased human myocardium. In addition, the mechanism of circulation during cardiac massage may be different (cardiac pump or thoracic pump mechanisms) in some species of animal or during different types of massage and this may influence the rate at which drugs injected peripherally reach the thorax. The ideal route is one which combines rapid access with speedy delivery of drug to the central circulation. There are four routes which have attracted the greatest attention.