This document discusses issues in single-subject research designs. It notes that while single-subject designs can have inherent rigor, not all studies using the designs are rigorous. It identifies some common threats to internal validity such as lack of treatment integrity and problems with baseline data. The document provides an overview of single-subject design elements and strategies to improve rigor, such as establishing clear criteria for participant selection, baseline stability, phase changes, and measuring clinically meaningful change through social validation. It emphasizes the importance of establishing methodological decisions a priori to reduce bias and threats to validity.