During the last 35 years he has investigated various aspects of the immune system. During the early 1970's he was the first person to demonstrate that cell-mediated immunity and antibody formation are mutually antagonistic responses, an observation that underpins the Th1/Th2 paradigm in immunology. He is currently attempting to harness immune deviation to produce novel anti-cancer vaccines. Since the late 1970's Professor Parish has also been interested in the role that complex carbohydrates, particularly heparan sulfate, play in cell adhesion and cell migration. These studies have resulted in heparanase, the enzyme that degrades heparan sulfate, being identified as a drug target and has formed the theoretical basis for the development of several carbohydrate-based drugs, such as PI-88 (Muparfostat), that inhibit inflammation, tumour metastasis and angiogenesis. In addition, Professor Parish’s laboratory has developed a number of important immunological techniques, such as fluorescent dyes (e.g., CFSE) for monitoring lymphocyte migration and proliferation. His research findings underpin several Australian biotechnology companies, such as Progen Pharmaceuticals and Lipotek. In 2005 Prof Parish was awarded the Clive and Vera Ramaciotti Medal for Excellence in Biomedical Research in recognition of his scientific achievements.