This study examined multidimensional item response theory (MIRT) modeling to assess social desirability (SocD) influences on self-reported physical activity self-efficacy (PASE) and fruit and vegetable self-efficacy (FVSE). The observed sample included 473 Houston-area adolescent males (10-14 years). SocD (nine items), PASE (19 items) and FVSE (21 items) were measured with previously validated self-report instruments containing Likert-type responses. Physical activity was objectively measured using the Computer ScienceApplicationIncorporated/Manufacturing Technology Incorporated (CSA/MTI) accelerometer. Total fruit, juice and vegetable consumption was measured with a food frequency questionnaire. Correlations between self-efficacy and behaviors were minimal, regardless of controlling for SocD. However, in a simulated sample derived to demonstrate the utility of MIRTwhen relationships exist, the pseudo-relationships between selfefficacy and behaviors were substantially weaker after controlling for SocD. MIRT provided disattenuated correlations between SocD and selfefficacy, thereby providingmore precise estimates of the real influence of SocD on the relationship between self-efficacy and behavior. However, as shown in the observed sample, more research is needed to understand the influence of SocD on the relationship between self-efficacy and behaviors for different populations and for different degrees of SocD response bias.