Cancer screening should be recommended only when the balance between benefits and harms is favorable. This review evaluated how U.S. cancer screening guidelines reported harms, within and across organ-specific processes to screen for cancer. To describe current reporting practices and identify opportunities for improvement. Review of guidelines. United States. Patients eligible for screening for breast, cervical, colorectal, lung, or prostate cancer according to U.S. guidelines. Information was abstracted on reporting of patient-level harms associated with screening, diagnostic follow-up, and treatment. The authors classified harms reporting as not mentioned, conceptual, qualitative, or quantitative and noted whether literature was cited when harms were described. Frequency of harms reporting was summarized by organ type. Harms reporting was inconsistent across organ types and at each step of the cancer screening process. Guidelines did not report all harms for any specific organ type or for any category of harm across organ types. The most complete harms reporting was for prostate cancer screening guidelines and the least complete for colorectal cancer screening guidelines. Conceptualization of harms and use of quantitative evidence also differed by organ type. This review considers only patient-level harms. The authors did not verify accuracy of harms information presented in the guidelines. The review identified opportunities for improving conceptualization, assessment, and reporting of screening process-related harms in guidelines. Future work should consider nuances associated with each organ-specific process to screen for cancer, including which harms are most salient and where evidence gaps exist, and explicitly explore how to optimally weigh available evidence in determining net screening benefit. Improved harms reporting could aid informed decision making, ultimately improving cancer screening delivery. National Cancer Institute.