» Australian Twin Registry    Includes a newsletter, registry for twins, study information and conferences.    http://www.twins.org.au/

» International Society for Twin Studies    Events, journal, bylaws, membership information.    http://www.ists.qimr.edu.au/

» Millennium Twins    A longitudinal sociological study of twins born in the new millennium.    http://www.millennium-twins.de

» Sleep Research Study for Twins    The University of Pennsylvania is recruiting same-sex twins living in the eastern time zone who are between the ages of 25 and 59 to participate in a sleep research study.    http://www.uphs.upenn.edu/sleepctr/clinicalresearch/twins.pdf

» The Center for Study of Multiple Birth    Recognized internationally as a unique resource for research and information about the causes, effects and problems of multifetal pregnancy.    http://www.multiplebirth.com/

» Twin Research    Journal of the International Society for Twin Studies. Topics covered in the journal include behavioral genetics, complex diseases, endocrinology, fetal pathology and other areas of research.    http://www.australianacademicpress.com.au/Publications/Journals/Twin_R/TResearch.htm

» Twin Research and Genetic Epidemiology    Located at St Thomas' Hospital, London, UK.    http://www.twin-research.ac.uk/

» Twin Studies    From the Institute of Behavioral Genetics at the University of Colorado. A handful of studies for twins of all ages.    http://ibgwww.colorado.edu/~agross/ibg/twinsites.htm

» Twins Personality Survey    A twin survey on personality, conducted by researchers at Virginia Commonwealth University.    http://www.outofservice.com/twins/