OBJECTIVES: To determine the therapeutical compliance in subjects with amlodipine and simvastatin substitution from mark to generic. Secondary objective: to know the professional and patient opinion about its use. METHODS: Patient and methods: Before-after design with control group, realized revision of the medical records, in six centres of primary care. Participants: Patients ≥ 40 years initiating treatment of mark drug (initial period) and after that had a substitution by generic (final period), between January 2003 and June 2009. Study groups: arterial hypertension (amlodopine) and Dislipemia (simvastatin). Main measures: Co-morbidity, compliance, treatment-time, biochemistry objectives and professional-patients opinion (interviews). Continuation: Beginning from the generic drug substitution date, each patient was (Minimum) one year before with a mark drug and a year after with and generic (minim continuation/patient: 24 months). RESULTS: A total of 1252 patients. Groups: 49.5% amlodipine; 50.5% simvastatin. Average age: 72.4 years; women: 48.9%. The ones treated with amlodipine (comparing periods); show a better compliance (65.8% vs. 61.3%; p=0.037) and arterial pressure control (48.5% vs. 45.8%; p=0.039) with mark drugs. With simvastatin, was 62.8% vs. 58.4%; p=0.041 (cholesterol control: 66.5% vs. 60.6%; p=0.032) respectively. Interviewed doctors: 73.6% prescribe generic and a 59.2% believe that both have the same efficacy. Interview patients: a 79.8% (CI: 74.3-85.3%) accepted substitution; a 55.3% (CI: 48.5-62.1%) received the appropriate information and 61.5% the different products confuse them. A 18.2% declare that abandon treatment. CONCLUSIONS: In patients with amlodipine/simvastatin substitution from mark to generics, it was observed less treatment compliance light, with minor consecution of control objectives. The realized interviews (professional/patients) reaffirm the results.