A major problem of market research units, in any field but we suggest particularly in industrial market research is to achieve the optimum rather than the maximum amount of data required, but with the maximum degree of precision necessary for the problem under consideration to be solved. We do not feel it necessary to say anything further about the question of achieving optima with respect to amounts of information. All we would add is that the postal questionnaire imposes a very severe discipline on the researcher in this respect. It may well be the case that the cost of asking for too much in the case of a postal questionnaire- when measured in terms of non-response rates - is greater than in the case of personal interviews. But what we believe to be more important is the possibility that, with respect to much of the quantitative data required in industrial market surveys, the postal questionnaire affords a better opportunity to the respondent to provide accurate information than is the case in very many personal interview situations. Indeed, not infrequently recourse is necessary to the provision of some sort of form, left with the respondent during a personal interview, by means of which, he subsequently returns the quantitative data required.