With the increasing prevalence of mobile technology and high-profile crashes bringing attention to distracted driving, data on cell phone involvement in collisions is critical for understanding the extent of the problem, examining the effectiveness of policies, and developing interventions to improve safety. Some limitations of existing data have been previously identified, but this paper examines the specific case of California’s collision data. Temporal, geographic, and jurisdictional trends are analyzed to identify the source and type of inconsistencies in the cell phone involvement data. Matching and comparison of state and federal data sources highlight further limitations. Data could be improved by simplifying the California crash report form and aligning variables to be more consistent with federal standards. In the meantime, it is not recommended that existing data on cell phone involvement in collisions be used for any analyses to evaluate policy or driver behavior.