Indiana University-Purdue University Indianapolis (IUPUI) / Ecological momentary assessment (EMA) has been asserted by proponents of the technique as being superior to standard paper-and-pencil measurements in terms of the reliability and validity of the information obtained; however, this claim has not yet been fully evaluated in the literature. Accordingly, the purpose of this study was to evaluate one aspect of this assertion by comparing the utility of EMA and retrospective measures of depressive symptoms in predicting health-relevant biological and behavioral outcomes. It was hypothesized that (1) the EMA measure will have better predictive utility when examining objective sleep quality (a biological outcome), and that (2) the retrospective measure will have better predictive utility when examining blood donation intention (a behavioral outcome). Ninety-six undergraduate females participated in this 2-week study. Depressive symptoms were measured momentarily and retrospectively using the Center for Epidemiological Studies-Depression Scale (CES-D). The biological outcome was assessed by actigraphy, whereas the behavioral outcome was measured via a self-report questionnaire. Unfortunately, it was not possible to fully test these hypotheses due to the failure to observe relationships between the predictor variables and the outcomes. The reported results, although limited, did not provide support for the hypotheses. Supplemental analyses revealed a moderate to high amount of shared variance between the EMA and retrospective measures, a similar extent of random error in both measures, and potentially a greater degree of systematic error in the retrospective measure. Due to the paucity of literature examining the claim of superior reliability and validity of EMA versus retrospective measures, as well as the failure of the current study to evaluate this assertion sufficiently, it appears that this claim remains unfounded. Therefore, suggestions for future research are provided.