Doctors and patients often think that the increasing number of adverse reactions and variable therapeutic effect are due to individual variability and quality of generic medicines. Wide-spread opinion among patients is that the original medicinal product is characterized by superior quality and effectiveness compared to generic products and also that there is difference in the quality among generic products. The aim of the present study is to evaluate the pharmaceutical quality of three generic products with modified-release containing the anti-diabetic active substance gliclazide and compare them with the original drug product Diaprel MR 60 mg modified-release tablets. The pharmaceutical quality of the chosen modified-release products containing 60 mg gliclazide was evaluated with respect to mass and uniformity of mass, resistance to crushing, friability and in vitro release behavior in three dissolution media. Also calculated was the factor of similarity. The results evidenced no significant difference in relation to pharmaceutical quality between the original and the generic products. All tested products complied with the requirements of Ph.Eur. in terms of mass and uniformity of mass and friability. The results obtained for resistance to crushing were similar. The dissolution behavior of the original and the generic products in the three dissolution media was also similar. A factor of similarity above 50 was achieved for all generic products in the three dissolution media. The study gives rise to confidence among patients when the original drug product is substituted with a generic drug product thus enhancing their compliance.