  In this study, we consider the notion of similar ruled surface for timelike
and spacelike ruled surfaces in Minkowski 3-space. We obtain some properties of
these special surfaces in E_1^3 and we show that developable ruled surfaces in
E_1^3 form a family of similar ruled surfaces if and only if the striction
curves of the surfaces are similar curves with variable transformation.
Moreover, we obtain that cylindrical surfaces and conoids form two families of
similar ruled surfaces in E_1^3.
