We sought to determine the incidence, prevalence, and life expectancy of Aicardi syndrome from 408 cases compiled from multiple international sources. Last known age ranged from less than 1 month to 42 years. The incidence rates per live births for the United States and The Netherlands were 1 per 105 000 and 1 per 93 000, respectively. The prevalence in the United States is greater than 853 cases, and the worldwide estimate is several thousand. Forty-five cases were deceased (age range, 1 month to 33 years), and the risk of death peaked at age 16. The probability of survival at 27 years of age was 0.62 (95% CI, 0.47-0.77). The risk of death by age follows other congenital neurological disorders with a wide range in severity of functional disability. The longer life expectancy found in our study hints at a higher functioning capacity in Aicardi syndrome and may inform counseling to families.