Asphyxiophilia, the desire for a state of oxygen deficiency in order to enhance sexual excitement and orgasm, is a very precarious form of sexual gratification. Asphyxiophilia has been difficult to document since it is mostly practiced in secrecy and solitude and is usually not discovered until the practitioner has been found dead. Most of the information about asphyxiophilia is found in police reports and medicolegal investigations by doctors of forensic medicine. Our study is based on information from 18 doctors of forensic medicine in Denmark, Norway, and Sweden. Six sources indicate similar frequencies (0.5-1 cases per million inhabitants per year) of observed deaths in Scandinavia. Although the frequency of observed deaths is different from the true mortality rate, this study gives a good illustration of the estimated prevalence. This accuracy is enhanced by the length of the observation periods (10-40 years).