The research programme which is the subject of this paper started 9 years ago, just before the introduction of a new ethical product into a therapeutic market which was certainly ready for expansion. The programme is still continuing and has entered its most interesting phase now that the product has reached a dominant status in its particular sector. The evolution of the programme has been a deliberately planned process, designed always to anticipate changes in marketing requirements. Much of the earlier work was mainly confined to measuring variations in the structure of the market, to monitoring and predicting the position of our product within it and to unsophisticated enquiries into attitudes. The more recent work has been primarily concerned with the unravelling of more complex determinants of prescribing behaviour in order to reveal ways in which the remaining potential of our product may be realised.