Dallas is a cancer epidemiologist and is a co-investigator on the Melbourne Collaborative Cohort Study. The MCCS program includes studies of lifestyle factors such as diet, obesity, hormones and genetic variants. Within the MCCS, his research interests include the epidemiology of breast cancer, colorectal cancer and prostate cancer and of gastro-oesophageal reflux disease. He also leads work on vitamin D in relation to cancer, diabetes and mortality. He is a principal investigator on the Australian Longitudinal Study on Male Health, a new initiative funded by the Australian Government's Department of Health and Ageing that is based in the Melbourne School of Population Health. This study focuses on identifying the social determinants of male health.