Williams Syndromföreningen i Sverige
- The Williams Syndrome Association in Sweden, with a description of the disease and available for support for the afflicted.
- http://www.williams-syndrom.se/

The Williams Syndrome Foundation (UK)
- Providing information about the condition, and support and help to UK-based WS families.
- http://www.williams-syndrome.org.uk/

Williams Syndrome Foundation
- Seeks to create or enhance opportunities in education, housing, employment and recreation for people who have Williams Syndrome and other related or similar conditions.
- http://www.wsf.org

Williams Syndrome Association of Ireland
- Describing fund-raising and annual events for those with WS.
- http://www.wsai.ie/

Williams Syndrome Association in Romania
- Supporting WS families in Romania.
- http://www.williams-syndrome.ro/

Williams Syndrome Association
- Offers information and support to patients, their families and caregivers. Includes news and events, teacher and doctor information, regional services, WS listserve, and members area.
- http://www.williams-syndrome.org/

Le syndrome de Williams et Beuren
- French Williams Syndrome Association, with limited information in English, Italian and Spanish, and much more in French. Gives background of the organization, how to join, and clinical trials
- http://www.autourdeswilliams.org/

Hungarian Williams Syndrome Association
- Powerpoint slides describe the association in English; other content in Hungarian.
- http://www.williams.ngo.hu/

Federation of European Williams Syndrome Associations
- Coordinating the research and other activities of the national Williams Syndrome associations.
- http://www.euwilliams.org/

Canadian Association For Williams Syndrome
- Non-profit society dedicated to advancing research, education, and support. Includes about WS, resource centre, new parents, events and benefits, and how to help.
- http://caws.sasktelwebhosting.com/index.html

Belgian French Speaking Williams Syndrome Association
- Describes the purpose of the association, with much more content in French.
- http://www.syndromedewilliams.be/