This commentary discusses 4 issues relevant to interpretation of A. S. Green, E. Rafaeli, N. Bolger, P. E. Shrout, and H. T. Reis's (2006) article: (a) Self-reported compliance in medical settings has generally been substantially higher than verified compliance, suggesting that this is not a rare phenomenon; (b) none of the studies reported in Green et al. explicitly verified paper diary compliance; (c) the impact of participant motivation on diary compliance is unknown, and it may be difficult for researchers to accurately assess it in their own studies; and (d) without objective verification of diary compliance, analysis of the effects of noncompliance on data quality is difficult to interpret. The authors conclude that compliance in paper diaries and the effects of noncompliance on data quality are still unsettled issues.