Single-case research methods provide the basis for evaluating effective instructional approaches in special education. The purpose of this article is to provide special educators an overview of single-case research methods, with an emphasis on how these designs are used to establish whether an instructional practice relates to improved learner outcomes. Specifically, we describe (1) core principles of single-case design (SCD) research, (2) two frequently used SCDs--withdrawal and multiple-baseline designs, (3) how visual analysis of graphed data is used to examine functional relations in SCDs, (4) limitations to the generalizability of findings from individual SCD studies, and (5) two studies in the special education literature that use SCDs. Our take-home message is that SCDs can be used to determine whether an instructional intervention causes improved outcomes for students, but caution is warranted when generalizing results from individual SCD studies.