The Interdisciplinary Qualitative Research Subcommittee (IQRS) of the Task for on Evidence-based Interventions in School Psychology assumed the responsibility of developing criteria for reviewing qualitative methods used in intervention research. The IQRS, composed primarily of psychologists and anthropologists, was confronted with the long-standing debate between qualitative and quantitative researchers and with the task of explicating the potential contributions of qualitative research to establishing an evidence base for interventions in school psychology. Consequently, the outcomes of the subcommittee's work included not only a set of criteria for evaluating qualitative research but also a clearer understanding of the added value of mixed qualitative-quantitative approaches to intervention research. The purposes of this article are to provide an overview of qualitative research, present the criteria set forth by the IQRS, discuss the role of qualitative research in establishing the foundation for evidence-based practice, and introduce the illustrative research articles of the special issue. The four studies highlighted in this issue represent applications of qualitative research that meet the IQRS criteria and demonstrate the potential of qualitative research, conducted within a mixed-method framework, for enhancing our understanding of school-based interventions.