We use Gaia (DR1, DR2) stellar proper motions to study the kinematics of OB-associations. The average one-dimensional velocity dispersion inside 18 OB-associations with more than 10 Gaia DR1 stars is σv = 3.9 km s−1. The median virial and stellar masses of OB-associations are equal to 7×105 and 9 × 103 solar masses, respectively. The median star-formation efficiency is ε = 2.1%. We have found the expansion in several OB-associations. Models of the Galaxy with a two-component outer ring R1R2 can reproduce the average residual velocities of OB-associations in the Perseus, Sagittarius and Local System complexes.