Calcium channel blockers are most commonly used in hypertensive patients in Japan. However, information on the efficacy and safety of generic calcium channel blockers is insufficient. The objective of the present study was to retrospectively evaluate the efficacy and safety of manidipine hydrochloride in 21 essential hypertensive patients (mean age; 70.6+/-10.6 years, male/female; 14/7) in Sendai Postal Services Agency Hospital who were switched (substituted) from a brand product (Calslot) to a generic product (Manidip). For this retrospective study, we used data from patient medical records and drug prescription information. Data from patients who were taking both types of manidipine hydrochloride, whose regimen were not changed for > 6 months before and after switching, and who provided informed consent were included in the analysis. Control values of blood pressure were not significantly different between before and after substitution (systolic/diastolic; from 137.9+/-9.1/78.7+/-5.4 mmHg to 137.3+/-9.1/77.8+/-6.3 mmHg, p=0.73/p=0.36). The level of patient compliance for the antihypertensive drugs was also not different between before and after substitution (from 94.0+/-8.8% to 93.1+/-9.6%, p=0.72). There were 8 cases of adverse effects before substitution and 4 after substitution. No patient stopped taking the generic drug due to an adverse effect. In conclusion, significant differences in the efficacy, safety, and patient compliance were not observed between the brand product and generic product among patients who were switched from the brand product to the generic product.