Information about events which happen with great regularity are, individually, of such small importance that no individual could be relied on to list them accurately from memory. But each individual event, when added together, can have very important implications from a marketing point of view. In order to collect data related to such events, we have used a diary technique - asking an individual, generally the housewife, to ensure that a complete record is kept of each event over a limited period - not only for those events for which she, herself, is responsible but also for all those involving other members of the household. In this paper, we shall-refer to some cases where this technique has been used successfully, and also discuss briefly, some of the pitfalls which might occur. We shall emphasize that this is an ad hoc technique, but it does not replace the more usual ad hoc surveys using normal aided or un-aided recall methods. It is a slightly more expensive tool to be used for problems where memory failure is likely to be acute, and where data are required from all household members, rather than from an individual within the household.