Occupational studies of aircrew in civil or military aviation did not receive much attention until the beginning of this decade. Since 1990, a number of epidemiological studies has been published on the cancer risk among flight personnel. Their results are equivocal: elevated cancer risks have been observed in some studies, but not in others. The exposure situation for pilots and flight attendants is unique with respect to several factors and particularly in that cosmic rays contribute substantially to their cumulative radiation dose. The average annual doses received are relatively low, however, and commonly range between 3 and 6 mSv. Results of epidemiological studies are presented as well as information on planned studies.