Active learning is a popular approach to teaching and learning that has gained traction through research on STEM educational improvement. There have been numerous university- and national/international-level efforts focused on transitioning courses from the lecture method to active learning. However, despite these large-scale changes, the active learning literature has not been assessed on its methodological rigor to ensure instructional recommendations are rooted in rigorous research studies. The purpose of the present review was to determine areas of strengths and areas in need of improvement and to provide specific recommendations on how to continue or improve active learning research to strengthen the respective literature base and increase confidence in results. We assessed the articles included in the Freeman et al. (PNAS, 111:8410-8415, 2014) meta-analysis as well as a random sample of more recent active learning articles (2015-2022) on 12 internal validity controls (i.e., control procedure used to prevent a threat to the internal validity of a study). Results indicated that there were high percentages of articles that did not meet each internal validity control. In fact, no articles from the Freeman et al. meta-analysis and no sampled 2015-2022 articles met each of the 12 internal validity controls. Therefore, the active learning literature contains numerous internal validity control issues that need to be addressed if we are to determine the extent to which active learning interventions are effective and if there are any boundary conditions for when particular active learning interventions are or are not effective.