The analogy between economics and medicine is sometimes a useful one. In medicine, progress is often made first through an improvement in understanding of a certain disease and then by improvements in treatment of the underlying causes of the disease and through preventive measures such as improvements in standards of hygiene. Similarly in economics, many ‘diseases’ which were apparently poorly understood by policy makers in the past – such as the hyperinflation which results from persistent recourse to the inflation tax through strong expansion of the money supply – have now been largely eradicated in industrialised countries; the IMF Mission Chief knows how to treat the hyperinflation of a programme country, and the Central Bank Governor knows how to avoid one. On the other hand, the medical profession has found it difficult to find a means of preventing orcuring some diseases, and economists, too, have found certain economic diseases – in particular speculative attacks on exchange rates – hard to find a panacea for. In the interesting chapter 9 by Glick and Rose, the authors seek to improve our understanding not of the underlying causes of the speculative-attack disease, but of the way in which the disease is transmitted from one victim to another, in other words the contagion of speculative attacks.