The purpose of the present epidemiological study is to investigate and describe panic disorder and sporadic panic attacks among a cohort of young adults, aged 28 years, from the Canton of Zurich in Switzerland. Both DSM-III panic disorder and sporadic panic are characterized by frequent symptoms of somatic anxiety and tension, as well as by frequent symptoms of depressed mood and low vitality. Sporadic panic is more prevalent than panic disorder and shows a greater excess of females over males. The association with depressions (major depression and recurrent brief depression) is similarly high for both types of panic syndromes, while the association with other anxiety disorders is negligible. Several indicators suggest a marked similarity between sporadic panic and DSM-III panic disorder. More impressive differences were observed between subjects with panic disorder alone and subjects with comorbidity of panic and depression. For the latter group, the SCL-90R scores indicated higher severity. Comparison of the scores of life events, conflicts, self-esteem, and the number of chronic problems in childhood suggests a more specific nosological pattern for subjects with panic and depression as compared with those with panic alone.