Primary care patients with infrequent panic attacks were found to have similar levels of disability in their social, family and vocational functioning to patients who met DSM-III-R criteria for panic disorder. Both panic subgroups had significantly more functional disability than controls. Patients with panic and infrequent panic had significantly more Axis I psychiatric comorbidity than primary care controls but similar levels of medical comorbidity. Patients with panic disorder had a significantly higher prevalence of one or more other lifetime psychiatric diagnoses, current major depression, and current DSM-III-R depressive symptoms compared to patients with infrequent panic. Patients with infrequent panic scored as high on the NEO personality measure of neuroticism as patients with panic disorder, and both panic subgroups had significantly higher neuroticism levels than controls.