  The quark gluon plasma generated in ultrarelativistic heavy ion collisions
may possess sizable momentum-space anisotropies that cause the longitudinal and
transverse pressures in the local rest frame to be significantly different. We
review recent attempts to derive a dynamical framework that can reliably
describe systems that possess a high degree of momentum-space anisotropy. The
dynamical framework that has been developed can describe the evolution of the
quark gluon plasma ranging from the longitudinal free-streaming limit to the
ideal hydrodynamical limit.
