Investigators have found a relationship between the number of previous alcohol withdrawals (AWs) and severity of withdrawal. We evaluated patients with multiple previous AWs, as compared to those with 0-1 previous withdrawals, in an outpatient detoxification trial comparing lorazepam (LZ) to carbamazepine (CBZ). A mixed model analysis of covariance was used to analyze Clinical Institute Withdrawal Assessment for Alcohol-Revised (CIWA-Ar) scores as a function of detoxification history (0-1 vs. 2 or more), drug group (CBZ vs. LZ), assessment day, and hours since last drink. The mixed model analysis of covariance (ANCOVA) indicated a significant detoxification history by assessment day interaction (P< or =.03). Least square means associated with this interaction suggested that the CIWA-Ar scores for the multiple detox patients declined more slowly than those with 0-1 previous detoxifications. Patients with multiple detoxes were 150% more likely to experience a heavy drinking day during treatment (P< or =.03). The multiple detox group drank more each drinking day (P=.001) and a greater proportion of this group had early heavy drinking (P=.0002). In the present study, intensity of AW symptoms and early heavy drinking were independent of treatment medications and were more common in patients who had previously undergone multiple treatments for AW.