Single-subject designs provide the special education field with an alternative to group designs. The purpose of this paper is to introduce the topic of single-subject designs by providing an overview of the relevant literature and a discussion of the major issues and applications of these designs in the field of special education. This paper is divided into four main sections: (1) characteristics of single-subject designs; (2) types of single-subject designs; (3) advantages of single-subject designs; and (4) issues and concerns regarding single-subject designs. It was concluded that a minimum of three measurements in each phase is typically required until there is a clear pattern. Flexibility and cost-effectiveness are among the main advantages of these designs. External validity and generalisability are the main concerns. However, meta-analytic studies can enhance the generalisability of single-subject designs findings within similar context. Conclusions and recommendations to improve these designs are discussed.