  Disks of collisionless particles are important models for certain galaxies
and accretion disks in astrophysics. We present here a solution to the
stationary axisymmetric Einstein equations which represents an infinitesimally
thin dust disk consisting of two streams of particles circulating with constant
angular velocity in opposite directions. These streams have the same density
distribution but their relative density may vary continuously. In the limit of
only one component of dust, we get the solution for the rigidly rotating dust
disk previously given by Neugebauer and Meinel, in the limit of identical
densities, the static disk of Morgan and Morgan is obtained. We discuss the
Newtonian and the ultrarelativistic limit, the occurrence of ergospheres, and
the regularity of the solution.
