The International Workshop on HIV and Hepatitis Observational Databases (IWHOD) brings senior and junior HIV and hepatitis observational database researchers together to advance the methodology and analysis of observational data. No other workshop or conference devotes attention to the methodology of setting up and analyzing observational data, despite their importance in providing critical information on population outcome in real world settings outside the controlled setting of randomized trials. We are once again aiming to include attendees representing cohort studies from all regions. As in the past, we encourage discussion of work in progress, so all data presented will not be publicised outside of the Workshop.