OBJECTIVE: To analyse the costs and the effectiveness of an intervention of home visits made by nurses to elderly people versus usual care given by the family medicine units. MATERIAL AND METHODS: A sample of 4,777 subjects aged 60 years and over covered by the Mexican Institute of Social Security (Instituto Mexicano del Seguro Social, IMSS) were screened. Those with a systolic and/or diastolic blood pressure level higher or equal than 160/90 mm Hg were randomly allocated to the intervention or control groups. The intervention consisted of visits at home by nurses who gave health and lifestyle advice to the participants. The economic evaluation was considered from a health services and patient perspective. Direct and indirect costs were calculated as incremental. Effectiveness was measured in terms of cost per millimetre of mercury reduced. RESULTS: Three hundred and forty five participants were allocated to the intervention group and compared with 338 controls. At the end of the intervention period the difference in the mean change in systolic blood pressure was 3.31 mm Hg (95% CI 6.32, 0.29; p = 0.03) comparing with the control group. In diastolic blood pressure the difference was 3.67 (95% CI 5.22, 2.12; p < 0.001). The total cost of the intervention was 101 901.66 pesos. The intervention cost per patient was 34.61 pesos (US$3.78), (CI 95% 34.44, 35.46). The cost-effectiveness ratios was 10.46 pesos (US$1.14) for systolic (CI 95% 129.31, 5.51) and 9.43 (US$1.03) for diastolic (CI 95% 19.90, 2.49). CONCLUSIONS: The reduction in blood pressure obtained may well justify the small incremental cost of the intervention.