He has published more than 700 papers, specialising in the statistical methodology and its application for analysing twin and family data, and addressing the genetic and environmental aetiology of diseases and health. He is principal or co-investigator on a number of case-control-family studies across a range of diseases and conditions, particularly breast cancer and colorectal cancer (both funded by the National Institutes of Health (USA)), prostate cancer, melanoma, childhood cancer and asthma. He is a co-investigator on several cohort studies, including Health 2020 and long term follow-up of the 1968 Tasmanian Asthma Study.