Conservative management of acute type B aortic dissection (ABAD) is often associated with aortic dilatation during follow-up increasing the risk of aortic rupture. The goal of this study was to investigate whether morphologic characteristics of the dissection can predict aortic growth.All conservatively managed ABAD patients from four referral centers were included (2000 to 2010). Aortic diameters were measured at five levels at baseline and at the last follow-up computed tomography angiography, and annual aortic growth rates were calculated for all segments. Linear regression was used to study the influence of aortic morphologic characteristics for aortic dilatation.Included were 62 patients (41 men) with a mean age of 60.3 ± 10.7 years. Among the 310 analyzed aortic segments, 248 (80.0%) were dissected, of which 211 (85.1%) showed aortic growth. Overall, the mean diameter increased from 36.1 ± 9.4 to 40.2 ± 11.1 mm (P < .01), which corresponds with a mean aortic growth rate of 3.1 ± 6.3 mm/y. Multivariate linear regression analysis showed that male sex (95% confidence interval [CI], 0.60-4.04; P = .005) and a saccular false lumen (95% CI, 2.07-7.81: P = .001) were associated with a significantly increased aortic growth rate. Increasing age (95% CI, -0.23 to -0.04; P = .005), increased number of entry tears (95% CI, -2.40 to -0.43; P = .005), false lumen located on the aortic outer curvature (95% CI, -4.30 to -0.38; P = .019), and a circular configuration of the true lumen (95% CI, -5.35 to -0.32; P = .027) were associated with a decreased aortic growth rate.Multiple morphologic characteristics appear to predict aortic dilatation in ABAD patients treated medically. Early assessment of these morphologic signs may be useful in the selection of ABAD patients who might benefit from closer radiologic surveillance or prophylactic intervention.