Prescribing costs in general practice continue to grow. Their importance is underlined by the amount of information concerned with costs that general practitioners (GPs) receive, and by the existence of target budgets. In 1986 and 1991, surveys showed that GPs agreed that cost should be borne in mind when choosing medicines, but that their knowledge of drug prices was often inaccurate. This study assessed the current knowledge and attitudes of GPs in the UK in respect of prescribing costs, and examined the influence of various developments in general practice since 1986 on the accuracy of drug price estimation. 1000 randomly selected GP principals (500 in Scotland and 125 in each of 4 English health regions) were sent a postal questionnaire. The GPs' level of agreement with 5 statements concerned with prescribing costs, and the accuracy of their estimates of the basic price of 31 drugs, were analysed. Most GPs (71%) agreed that prescribing costs should be taken into account when deciding on the best treatment for patients. Fundholders were more likely than non-fundholders: (i) to agree that prescribing costs could be reduced without affecting patient care; (ii) to agree that providing more information on costs would lower the cost of prescribing; and (iii) to comment that cost guidelines had changed their prescribing habits. Fundholders were less likely than non-fundholders to reject the principle of fixed limits on prescribing costs. Overall, one-third of the price estimates given were accurate (within 25% of the actual cost). For the most expensive drugs in the survey [those priced over 10 pounds sterling (Pound) per pack], half of the price estimates were accurate. There were significant differences between non-fundholders' and fundholders' estimates of the price of less expensive drugs (those priced at less than 10 pounds per pack). Use of a formulary or computer-displayed drug price information did not affect the accuracy of price estimates. It may be that GPs who were more knowledgeable and concerned about costs were more likely to become fundholders. It is also possible that the expansion of fundholding, or other mechanisms that give GPs responsibility for resource allocation, might improve accurate cost awareness in prescribing. Clinical and economic review of repeat prescribing is recommended.