Colourful polygons surround the OHTN Cohort Study Logo

The OHTN Cohort Study

The Ontario HIV Treatment Network Cohort Study (OCS) is a community-governed, province-wide research study aimed at improving the health and well-being of Ontarians living with HIV. Established in 1996, over 3,700 individuals actively participate at nine HIV clinics across the province.

The OCS promotes clinical, psychosocial and socio-behavioural research to inform government policy, clinical practice and other care and support services. OCS team members work with leaders in the fields of HIV/AIDS, hepatitis C and other sexually transmitted and bloodborne infections.

About the Cohort       

Since 1996, over 6,400 participants have participated in the OCS. The OCS is the largest HIV cohort in Ontario and one of the largest in North America.

The cohort represents a diverse group of Ontarians living with HIV including men and women of different ages, sexual orientations and ethnicities.

A 2015 study assessing engagement in care among OCS participants between 2001 and 2011 found that 87% of participants were receiving regular viral load and CD4 tests; 77% were taking antiretroviral medication; and 76% had a suppressed viral load. You can read more about the study here.

Join the Cohort

If you were diagnosed with HIV between 2011 and 2016 and attend a participating OCS clinic, please talk to your doctor or nurse about how you can join. A list of participating clinics is available here.

OCS Research

Plain language fact sheets summarizing recent research findings are available on the following topics:

Information for Researchers

Researchers can access OCS data by completing the following steps:

  1. Submit an OCS Concept Sheet or an OCS-ICES Concept Sheet
  2. Request a Data Scan
  3. Develop a research proposal using the Research Project Proposal Checklist
  4. Sign an OCS Researcher Confidentiality Agreement
  5. Undergo scientific, community and ethical reviews.

The OCS Research Coordinator can answer any questions you have about this process.


OCS acknowledgements are available in PDF and PowerPoint formats.


For additional information, contact Madison Kopansky-Giles, OCS Coordinator: mgiles [at], 416.642.6486, x. 2224.

Study Partners

The OHTN Cohort Study collaborates with Public Health Ontario, the Canadian Observational Cohort Collaboration (CANOC), the North American AIDS Cohort Collaboration on Research and Design (NA-ACCORD), and the Institute for Clinical Evaluative Sciences (ICES).