Objectives: Although family members of patients with aortic dissection (AoD) are believed to be at higher risk of AoD, the prognostic value of family history (FH) of aortic dissection (FHAD) in family members of patients with AoD has not been studied rigorously. We seek examine how much a positive FHAD increases the risk of developing new aortic dissection (AoD) among first-degree relatives. Methods: Patients with AoD at our institution were analyzed for information of FHAD. Positive FHAD referred to that AoD occurred in index patient and one or more first-degree relatives. Negative FHAD was defined as the condition in which only one case of AoD (the index patient) occurred in the family. The age at AoD, exposure years in adulthood before AoD, and annual probability of AoD among first-degree relatives were compared between patients with negative and positive FHADs. Results: FHAD was positive in 32 and negative in 68 among the 100 AoD patients with detailed family history information. Mean age at dissection was 59.9 +/- 14.7 years. Compared to negative FHAD, patients with positive FHAD dissected at significantly younger age (54.7 +/- 16.8 vs 62.4 +/- 13.0 years, p = 0.013), had more AoD events in first-degree relatives (2.3 +/- 0.6 vs 1.0 +/- 0.0, p < 0.001), and shorter exposure years per AoD event (18.3 +/- 6.7 vs 43.1 +/- 8.5, p < 0.001). Annual probability of AoD per first-degree relative was 2.77 times higher in patients with positive than negative FHADs (0.0100 +/- 0.0057 vs 0.0036 +/- 0.0014, p < 0.001). Conclusions: A positive FHAD confers a significantly increased risk of developing aortic dissection on family members, with a higher annual probability of aortic dissection, a shorter duration of "exposure time" before dissection occurs and a lower mean age at time of dissection. (C) 2017 Elsevier B.V. All rights reserved.