The role of genetic factors in panic disorder (PD) and sporadic panic attacks (SPAs) was investigated. A total of 120 twins recruited from the general population were interviewed for the presence of anxiety disorders and SPAs. A significantly higher concordance among MZ than DZ twins was found for PD (73% vs. 0%) but not for SPAs (57% vs. 43%). These results confirm a significant role of genetic factors in PD but suggest that genetic factors might not be crucial for the development of SPAs.