Single case research designs (SCRDs) are integral to identifying evidence-based practices (EBPs) for young children with autism spectrum disorder (ASD); however, the field lacks guidance on measuring response maintenance within SCRDs. We identified 103 studies in which researchers used SCRD to investigate the maintenance of behavioral intervention outcomes for children with ASD ages 0-5. Findings include: (a) maintenance conditions across most EBP categories, (b) limited within-case replication of maintenance assessment, (c) inconsistent use of maintenance terminology, (d) varying frequencies of maintenance assessment, and (e) wide range in latency to first and last maintenance probe. Results indicate a pressing need for the regular inclusion of maintenance conditions in behavioral research to increase our understanding of programming for and assessing maintenance.