A class of solutions of the gravitational field equations describing vacuum
spacetimes outside rotating cylindrical sources is presented. The spacetim
e metric for this class is given by equation (35); to render this metric ex
plicit, one must solve the nonlinear differential equation (31). A subclass
of these solutions could correspond to the exterior gravitational fields o
f rotating cylindrical systems that emit gravitational radiation. This clas
s has a special solution-corresponding to the exact solution (32) of equati
on (31)-in common with the Robinson-Trautman gravitational wave spacetimes,
namely, the Siklos solution. The properties of rotating gravitational wave
s are briefly investigated. In particular, we discuss the energy density of
these waves using the gravitational stress-energy tensor.