Abstract The current study applies the growing literature in the organizational sciences regarding levels of analysis issues to the analysis of substance abuse treatment beliefs. Research on clinicians' beliefs in substance abuse treatment is often based on the assumption that the beliefs are sufficiently shared by clinicians within a clinic and sufficiently vary across clinics that they can be treated as a group-level phenomenon. Further, efforts to introduce new innovations are often focused at the group or clinic level without testing this assumption, which can lead to failure to adopt or to successfully implement the innovation. We tested the assumption of sharedness by examining if there was sufficient agreement about treatment beliefs within clinics, within groups of clinics or within groups of clinicians to justify treating these aggregations as meaningful groups. Using three statistical approaches to examining level of analysis (Within and Between Analysis (WABA I), Intraclass Correlation Coefficients (ICC(1)), and r wg), we found that variability in treatment beliefs largely occurred at the individual rather than at the tested aggregate levels of analysis. These findings serve as an example of the importance of testing the assumption of shared perceptions in future research.