Costs were not reported as discounted. The difference in the acquisition costs of enalapril and benazepril was estimated by multiplying the monthly change by the number of months since switching for each of the 1,500 patients in the programme. The costs of the programme were also estimated. These included the costs of additional antihypertensive therapy following switching therapy, discarded enalapril tablets following the switch, changes in the number of clinic visits, laboratory costs and pharmacists' time. The cost of the initial clinic check to determine blood pressure was included in costs. The costs of a clinic visit were estimated by determining the amount of time spent by each member of staff during a visit. These estimates were determined by a questionnaire. Future clinic visits were not included in the costs of the programme since the time between visits did not differ "significantly" (p</=0.05) from that when using enalapril. Costs of changes in antihypertensive therapy were not included if the patient had experienced uncontrolled blood pressure whilst on enalapril, had received a higher amount of antihypertensive therapy whilst on enalapril, or had received a lower dosage of benazepril than was equivalent to the dose of enalapril previously received. For those patients with comparable antihypertensive regimens before and after the switch, the drug costs for changes in non-ACE-inhibitor regimens were excluded because they were considered to be common to both periods. The price year was not stated.