MedlinePlus Medical Encyclopedia: Klinefelter Syndrome
- Defines this condition, the causes, symptoms, treatment, prognosis, and complications.
- http://www.nlm.nih.gov/medlineplus/ency/article/000382.htm

Yahoo!: XXYList
- XXY is a genetic anomaly which occurs 1 in 500 in the general population today. Men with this condition usually have Klinefelters Syndrome. Offers joining instructions for this support group.
- http://groups.yahoo.com/group/xxylist

XXY Information (Klinefelter Syndrome)
- Medical information, news, and links.
- http://www.47xxy.org/XXYframe.html

Turner Center
- Literature on XYY, Klinefelter, XXX, and Turner's Syndrome.
- http://www.aaa.dk/turner/engelsk/

American Association for Klinefelter Syndrome Information and Support (AAKSIS)
- Email list, conference, membership, newsletter, regional groups and resource links.
- http://www.aaksis.org/

Genetic Org Home
- Information about Klinefelter Syndrome, when it was first discovered, the common characteristics, and treatment.
- http://www.genetic.org/

Klinefelter's Syndrome gynecomastia
- Male chest recontouring for large male breasts (gynecomastia) found in Klinefelter's Syndrome with surgical reduction by excision and liposuction. Before and after photographs, links, movies, and patient question and answer boards.
- http://www.plasticsurgery4u.com/procedure_folder/male_breast4.html

Klinefelter Syndrome
- Overview and medical information.
- http://www.emedicine.com/PED/topic1252.htm

XXY List
- A private discussion list for which you must be an XXY to subscribe.
- http://www.globalwebsol.com/xxy

Klinefelter Syndrome Support
- Educational and support information about Klinefelter Syndrome/XXY and its variants.
- http://klinefeltersyndrome.org