The study of hadron production in heavy ion collisions is essential to the search for effects beyond independent nucleon-nucleon collisions, for example the predicted phase transition to quark matter. Hadron distributions are known over a large range of transverse momenta for p-p collisions, so a careful study of the differences can be made. The transverse momentum distributions of hadrons may provide global information about p-nucleus and nucleus-nucleus collisions, such as the degree of thermalization achieved, and perhaps provide evidence for collective expansion of the highly excited central region. Comparison of the p{sub t} and transverse mass, m{sub t}, distributions of different hadronic species are crucial to extract this kind of information. Hadronic p{sub t} spectra show effects of the collision dynamics, such as hard scattering processes, and possibly rescattering of partons as well as of the formed hadrons. Such modifications have been observed in p-nucleus collisions, and can be expected to be important in nucleus-nucleus reactions. The spectral shape changes arising in this manner cause a background in efforts to extract global information from hadronic p{sub t} spectra. Lastly, there is an excess of pions observed at low p{sub t} in p-A and A-A collisions. the origin of these soft pions is not yet well understood. The phenomenon represents a major difference between p-p and nuclear collisions. 31 refs., 8 figs.