Lag schedules increase operant variability. Several researchers have explored their clinical and educational applications, especially to address repetitive behavior or limited repertoires in individuals with autism spectrum disorder. In the current study, we provide the first comprehensive synthesis and appraisal of lag schedule research in humans. A multistep search strategy was employed to identify all experimental studies of lag schedules in humans published in peer-reviewed journals. We identified 38 studies that met inclusion criteria, summarized the study and participant characteristics, and evaluated evidential certainty. The results suggest that lag schedules are emerging as a promising applied behavioral technology for increasing operant variability, especially in individuals with autism spectrum disorder. We conclude with preliminary practice guidelines based on evidential certainty provided by the studies and identify future avenues of research.