This series of articles, which provide an overview of several advanced statistical methods for evaluating treatment outcomes and mechanisms of change, makes up the first research methods-oriented special issue to appear in the Journal of Consulting and Clinical Psychology. Like most active areas of scientific inquiry, the field of biostatistics and quantitative psychology continues to innovate and progress at a remarkable pace. These recent advancements provide researchers with the tools needed to ask and get answers to progressively nuanced and complex questions. It is our hope that the articles included in this special issue will spark an interest among applied researchers to investigate and learn how these and other newer statistical methods might be used to enhance their own line of research.