'Non-fearful panic disorder' (NFPD) is a condition that meets DSM III-R criteria for panic disorder but lacks a report of subjective fear or anxiety. Presenting the first comprehensive overview of this issue, the authors describe studies investigating a wide range of apparently overlapping phenomena including NFPD, 'somatically expressed panic', 'non-cognitive panic', 'alexithymic panic', 'non-clinical panic', and 'masked anxiety'. The review shows that such conditions account for from 20 to 40% of the panic disorder found in various medical populations, and that this group resembles conventional panic disorder in cross-sectional comparisons. We emphasize that a 'triple-response' model of anxiety is consistent with our conclusion that NFPD should be conceptualized as a panic disorder subtype. Finally, we discuss unresolved issues regarding the construct and predictive diagnostic validity of NFPD.