The objective of this study was to determine the efficacy of pindolol as an augmentor of fluoxetine in treatment-resistant panic disorder (PD). Twenty-five outpatients having PD with or without agoraphobia were included. These patients had not responded to two different trials with antidepressants and an 8-week trial of fluoxetine 20 mg/day. Treatment-resistant PD was defined as a less than 20% reduction in score on the Panic Self-Questionnaire (number of attacks per week) (PSQ) and the Clinical Anxiety Scale With Panic Attacks (CAS+PA). These patients continued to receive fluoxetine 20 mg/day and were randomly assigned to additionally receive either pindolol (2.5 mg three times daily) or placebo for the following 4 weeks. Evaluations were performed weekly using the Hamilton Rating Scale for Anxiety, the Hamilton Rating Scale for Depression (HAM-D), the CAS+PA, the NIMH Anxiety Scale, the PSQ, and the Clinical Global Impression Scale. The data were analyzed using a repeated-measures analysis of variance (ANOVA) and a t-test for independent samples. Patients treated with the combination of pindolol and fluoxetine (N = 13) demonstrated a significant improvement over the patients treated with fluoxetine and placebo on all rating scales, with the exception of HAM-D. The statistical differences were shown using the repeated-measures ANOVA (baseline, week 2, week 4) and also with t-tests from the second week of the trial. These preliminary results demonstrate that pindolol has an augmenting effect on fluoxetine in patients with treatment-resistant PD.