The present study examined the short-term stability of personality trait scores from the Revised NEO Personality Inventory (NEO-PI-R) among 230 opioid-dependent outpatients. The NEO-PI-R is a 240-item empirically developed measure of the five-factor model of personality (Neuroticism, Extraversion, Openness, Agreeableness, and Conscientiousness). Participants completed the NEO-PI-R at admission and again approximately 19 weeks later. Results indicated fair to good stability for all NEO-PI-R factor domain scores, with coefficients ranging from .68 to .74. Stability of NEO-PI-R scores was decreased among potentially invalid response patterns but was not significantly affected by drug-positive versus drug-negative status at follow-up.