We numerically and experimentally investigate a fishnet metamaterial operating at around 100 GHz. Qualitative effective medium theory and standard retrieval characterization methods are performed to demonstrate the double negative nature of the fishnet structure. This study is extended to include the effects of a finite number of unit cells at each layer and the number of layers in the propagation direction. Finally, we study the response of the metamaterial layer when the metamaterial plane normal and the propagation vector are not parallel.