Haemophilus parasuis is the causative agent of Glysser's disease in swine. Glysser's disease affects swine health and producer profits but the mechanisms through which disease occurs remain unclear. The primary objective of this dissertation research was to use molecular biology techniques to investigate the molecular basis of H. parasuis pathogenesis. To this end, four projects were carried out. Firstly, we generated a draft of an H. parasuis genome, the first made available to the public. Secondly, we identified and studied the genes of two outer membrane proteins possibly associated with virulence from 35 strains of H. parasuis. Thirdly, experiments to detect H. parasuis IgA protease activity were conducted. Finally, we developed an enhanced multi-locus sequence typing (MLST) system for the characterization of H. parasuis isolates. We established a publicly accessible database where current types may be viewed and to which new sequences may be submitted. Together, these studies provide insight into the workings of H. parasuis and establish a framework upon which future studies can be based. The information presented in this dissertation advances understanding and makes progress toward the development of enhanced treatment and prevention strategies.