"Dropouts" are a major concern when monitoring treatment efficacy in clinical trials.Alcohol-dependent patients are especially prone to discontinuing treatment, perhaps because of impulsive behavior. The Tridimensional Personality Questionnaire (TPQ) measures a trait-like quality, novelty seeking, which may reflect impulsiveness. We tested the hypotheses that higher TPQ Novelty Seeking subscale scores would be associated with increased rates of treatment dropout and increased risk for dropping out earlier. A total of 170 alcohol-dependent men who participated in a double-blind, placebo-controlled pharmacotherapeutic trial for decreasing relapse drinking completed the TPQ and were monitored until treatment dropout. Logistic regression and Cox proportional hazards models were used to (1) describe the relationship between the TPQ Novelty Seeking score and the dichotomous outcome variable, treatment dropout; and (2) assess the effects of a number of potential confounding covariates on the relationship between the risk factor, novelty seeking, and the time to the outcome event. The mean Novelty Seeking score was significantly higher among study dropouts compared with nondropouts (p = 0.003). Higher Novelty Seeking scores were associated with a higher adjusted odds ratio for dropping out (adjusted odds ratio = 1.07, 95% confidence interval [CI] = 1.00-1.15) and a higher adjusted hazard rate for dropping out earlier (adjusted hazard rate = 1.05, 95% CI = 1.00-1.09). The TPQ Novelty Seeking subscale score may identify a subgroup of alcohol-dependent men who are at risk for dropping out of treatment. This information may be useful for developing treatment plans to encourage these high-risk patients to remain in treatment. (J Clin Psychopharmacol 1999;19:51-56)