This paper explores SEC comment letters that address firms’ use of non-GAAP measures in 10- Ks, 10-Qs, and earnings releases. We investigate the determinants of firms’ receiving non-GAAP comments and the revisions to non-GAAP reporting undertaken by comment recipients. Firms that experience poor GAAP performance and highlight non-GAAP earnings are more likely to receive a non-GAAP comment. However, we find no evidence that firms reporting more favorable non-GAAP performance than GAAP performance are more likely to receive a non- GAAP comment. We find that after receiving a non-GAAP comment, firms are more likely to abandon non-GAAP measures. When firms continue to use non-GAAP measures, they provide more justifications for using these measures while also decreasing the measures’ prominence. However, there is no significant change in the amount of non-GAAP exclusions. Overall, our findings suggest that non-GAAP comments are mostly effective in disciplining firms whose presentation of non-GAAP measures does not conform to the rules.