Hereditary angioedema (HAE) is rare, disabling and sometimes life-threatening. The aim of this study is to describe its prevalence, symptomatology and treatment in Sweden. A total of 146 patients were identified; 110 adults and 36 children with HAE type I (n=136) or II (n=10), giving a minimal HAE prevalence of 1.54/100,000. All patients received a written questionnaire followed by a structured telephone interview. This report focuses on the 102 adults who responded. Females reported 19 attacks in the previous year vs. 9 for males (p<0.01), and females reported 10 days of sick leave vs. 4 days for males (p<0.05). For all treated acute attacks, plasma-derived C1-inhibitor concentrate (pdC1INH) (used in 27% of patients) had a good effect. For maintenance treatment, 43% used attenuated androgens and 8% used pdC1INH, which reduced their attack rate by more than 50%. In conclusion, the minimal HAE prevalence in Sweden was 1.54/100,000. HAE affected females more severely. Attenuated androgens and pdC1INH had a good effect on preventing attacks.