A theoretical and practical discussion took place some years ago about the selection of high risk groups for the implementation of preventive activities. Particularly important in this discussion was Geoffrey Rose’s seminal work.¹ In this work, Rose set out the main advantages and disadvantages of such a “high risk group” preventive strategy. In Rose’s words, it is a strategy with some clear and important advantages:

• The “high risk” strategy produces interventions that are appropriate to the particular individuals identified and consequently has the advantage of enhanced subject motivation.

• The “high risk” approach also offers a more cost effective use of limited resources and a more favourable ratio of benefits to risks.

Despite these advantages, the “high risk” strategy of prevention has some serious disadvantages and limitations. Firstly, as in all screening one is likely to meet problems with compliance, and the tendency is for the response to be greatest among those who are often least at risk of the disease; this, however, may be true for voluntary exposures, but not necessarily for occupational exposures. A second disadvantage is that this strategy is palliative and temporary. It does not seek “to alter the underlying causes of the disease but rather to identify individuals who are particularly susceptible to those causes”.¹ There is another, third, related reason why the predictive basis of the “high risk” strategy of prevention could be weak. It is well illustrated by data which relate breast cancer to parity and other reproductive factors. High risk women generate a relatively small proportion of the cases, too few to justify pre-screening for the identification of high risk women to whom to offer mammography. The lesson from this example is that a large number of people at a small risk may give rise to more cases of disease than …