Taste sensitivity may be a valid quantitative predictor of other kinds of reaction to the same drug by a given organism (Fischer and Griffin, 1963). Such a relationship in healthy subjects has been directly demonstrated for hyoscine butyl bromide (Joyce, Pan and Varonos, 1968), but the implications for the prediction of clinical response have apparently not yet been explored in a direct fashion. For example, in one group of female schizophrenics with a low taste threshold for quinine, a significantly lower dose of trifluoperazine elicited toxic effects than was the case in a group with a high taste threshold (Knopp, Fischer, Beck and Teitelbaum, 1966). But this study made, without testing, two important assumptions: first, that the dose necessary to produce toxic effects is positively correlated with the therapeutic dose; second, that the relationship between taste threshold and response to the drug is non-specific, so that the bitter substance quinine may serve as an indicator of response to any bitter-tasting centrally-active drug, or perhaps to any drug at all. The first of these propositions, though once fashionable, is certainly open to discussion; to accept the second would eliminate the interesting possibility of using differences in taste thresholds for a range of drugs to predict the drug to which the individual patient might best react.