During the past decade so many psycho tropic drugs have been produced that the psychiatrist is often faced with a bewildering choice; for some mental disorders no fewer than a dozen preparations claim to remove or alleviate the symptoms. The work of La Verne (1962, 1963) and Jacobsen (1963) has been of considerable value in providing a “compendium of psychopharmacological agents”—a comprehensive classification of psychiatric drugs to assist the prescriber. Nevertheless, there are seldom any clear or universally accepted indications within a class (e.g. antidepressives or antipsychotics) why one drug should be prescribed rather than another. Many preparations share a common basic chemical formula, such as the phenothiazines, and/or a common biochemical function, like the monoamine oxidase inhibitors. The manufacturers themselves, anxious to cover every therapeutic possibility, suggest such a wide range of possible indications that their product often becomes a broad spectrum panacea, inviting increasing scepticism from the physician and concealing any potential advantage it may have for alleviating a particular symptom. Since personal experience determines choice more positively than any number of published reports, the psychiatrist gives most new products an informal trial, but tends to settle down with a limited few of proved usefulness and empirically confirmed indications. This is not a particularly efficient method for obtaining one's personal range of chemotherapeutics, but it is the one most generally used in practice. Its disadvantage lies in the idiosyncratic nature of some drugs, which may work well in one patient but ineffectively, or even adversely, in the next. On the basis of a few short and unsatisfactory trials, sometimes of only one, a potentially useful preparation may be discarded in favour of an older well-tried alternative which may be less therapeutically effective in the long run.