Purpose The time course of adverse events is an important factor for patient management. Clinicians are better able to prepare patients for specific adverse events, which leads to better treatment adherence. Methods Adverse events were followed longitudinally for 6 months during the open-label phase of a relapse prevention trial with 264 patients with generalized anxiety disorder. Adverse events were assessed at each treatment visit using a 21-item checklist. Logistic regression modeling, continuation ratio modeling, and hierarchical linear modeling were used to determine whether adverse events led to early attrition and whether adverse events decreased in enrolled patients over time. Findings Adverse events were found to have decreased highly significantly during treatment. A highly significant race effect was found in that whites had a significantly higher adverse event rate than did nonwhites. Early attrition rates were predicted by presence of nausea and fatigue, late attrition by dizziness, nervousness, and sexual dysfunction.