The purpose of this research is to gain an understanding of the local environment and the dynamical evolution of poor clusters of galaxies and compact groups of galaxies. The high densities and low velocity dispersions which characterize these systems make then unique dynamically. This combination is expected to lead to rapid merging of galaxies creating an environment which ought to be effective in altering the initial properties of disk galaxies, especially their neutral hydrogen (HI) gas content. Poor clusters and compact groups provide us with an opportunity to study the dynamical evolution of galaxies within systems that are presumably at different stages of the merging process: compact groups on the verge of the merging, while poor clusters have experienced several mergers in the past. This research can lead to improving our understanding of small groups which are "natural laboratories" for studying the various physical processes which make galaxies evolve so rapidly and can shed light on the interaction of galaxies with each other. Correlations between the HI content of disk galaxies and the local environment in which they are found have demonstrated that the 21-cm spectral line of hydrogen is a powerful tool for studying groups. The local conditions within Morgan poor clusters will be probed directly by measuring the HI content of their disk population and comparing it to the average gas properties of rich clusters and loose and compact groups of galaxies. Extending the data base of HI masses and sensitive upper limits to include the unobserved groups in Hickson's sample of galaxies will give a complete description of the global gas properties of dense groups. Using the detected hydrogen in these groups, a map of its distribution and kinematics should provide clues about the degree of dynamical evolution and the physical compactness of these systems. The local environment, i.e. neighborhood, in which compact groups are found will also be studied in order to gain some insight into their origin and formation.
