The present article „The Concept of Design Defect” has been elaborated with the aim of defining the notion of „design defect”, regulated by the American legislators and researchers and not being stipulated by the doctrine and legislation of Republic of Moldova. This work is endowed with concrete examples concerning the design defect, which in comparison with the fabrication defect of are more complex and more difficult to detect. More than that, if the manufacture defect can cause the deficiency of a single good, the design defect causes the deficiency of the whole production line. The present paper also refers to the defect of conception of medicines, being presented as a special product it is difficult to demonstrate whether it is a drawback of the product or of its concept.