For over a decade, the failure to reproduce findings in several disciplines, including the biomedical, behavioral, and social sciences, have led some authors to claim that there is a so-called "replication (or reproducibility) crisis" in those disciplines. The current article examines: (a) various aspects of the reproducibility of scientific studies, including definitions of reproducibility; (b) published concerns about reproducibility in the scientific literature and public press; (c) variables involved in assessing the success of attempts to reproduce a study; (d) suggested factors responsible for reproducibility failures; (e) types of validity of experimental studies and threats to validity as they relate to reproducibility; and (f) evidence for threats to reproducibility in the behavior science/analysis literature. Suggestions for improving the reproducibility of studies in behavior science and analysis are described throughout. Keywords Reproducibility . Replication . Null hypothesis significance testing . Statistical power . Effect size measures . Statistical conclusion validity . Construct validityThe crucial role of replication is established in science generally. The undetected equipment failure, the rare and possibly random human errors of procedure, observation, recording, computation, or report are known well enough to make scientists wary of the unreplicated experiment. When we add to the possibility of the random "fluke," common to all sciences, the fact of individual organismic differences and the possibility of systematic experimenter effects in at least the