The OHTN Cohort Study

Established in 1996, the Ontario HIV Treatment Network Cohort Study (OCS) is the largest community-governed HIV cohort in Ontario and is one of the largest cohort studies in North America. It represents a diverse group of Ontarians living with HIV including men and women of different ages, sexual orientations and ethnicities.


The latest updates on the OHTN Cohort Study. Published papers, upcoming changes, etc.


Backgrounder on OCS practices, policies, participants and staff.


Research subjects, data access procedures, and our most recent publications.

Site Information


Information on the founding and evolution of the OHTN Cohort Study, including our GIPA/MIPA policy.

OCS by the numbers

15 years; 5644 participants; 27,720 person-years of observation.