The frequency with which patients fail to recall advice presented by their doctors is discribed. The amount forgotten is shown to be a linear function of the amount presented, to be correlated with the patient's medical knowledge, anxiety level and possibly age, but not with intelligence. It is probable that instructions and advice are more often forgotten than other information, and that this is the result of their low perceived importance, and their being presented late in the series of statements presented-there being (a) a primacy effect in recall of medical information, and (b) a tendency for statements perceived as more important to be better recalled. Experiments to control the content and amount of forgetting are described. Control of content can be obtained by use of the primacy and importance effects, while control of amount forgotten can be achieved by use of (a) simpler language, (b) explicit categorization, (c) repetition, and (d) concrete-specific rather than general-abstract advice statements.