The next move forward in simulations of cosmological structure is to include the hydrodynamics and thermal history of a gaseous component. The task is not an easy one. The dynamic range is wide in all interesting quantities (density, temperature, length-scales, time-scales, etc.). Generic initial mass distributions sampled from Gaussian random fields will, for many interesting power spectra, lead to a high degree of substructure present at all stages of the evolution. Grid-based hydrodynamic techniques currently lack the resolution necessary to evolve several levels of a clustering hierarchy simultaneously. A particle-based method known as SPH (Smoothed Particle Hydrodynamics, see Monoghan (1985) for a review) appears best suited for cosmological application. I have recently imbedded the technique into the P3M N-body code, described by Efstathiou et al. (1985) and used extensively by Efstathiou and collaborators, most recently in investigations of the cold dark matter scenario.