The National Malaysian Twin Registry was established in Royal College of Medicine, Perak, University Kuala Lumpur (UniKL) in June 2008 through a grant provided by UniKL. The general objective is to facilitate scientific research involving participation of twins and their family members in order to answer questions of health and wellbeing relevant to Malaysians. Recruitment is done via mass media, poster, and pamphlets. We now have 266 adult and 204 children twins registered. Several research projects including reproductive health study of twins and the role of co-bedding on growth and development of children are carried out. Registry holds annual activities for twins and seeks to provide health-related information for twins. We seek international collaboration.Keywords: Malaysia, reproductive health, twin, registry Research BackgroundThe Malaysian Twin Registry started with a reproductive health study that captured many aspects of reproductive health and reproductive behavior of adult twins. Publications of the study focused on age of menarche, premenstrual syndrome, menstrual characteristics, and reproductive health of opposite sex twins (Jahanfar, 2012a(Jahanfar, , 2012bJahanfar et al., 2011Jahanfar et al., , 2012. General ObjectivesThe aims of the Malaysian Twin registry are:• to establish a research foundation, that can bring researchers together to carry out research activities.• to provide a bridge between researchers and twins and public as a whole, who will ultimately benefit from the result of these studies.• to collect, preserve, and communicate information about twins and other multiples.• to convey information of interest to twins and educate twins regarding health issues.• to establish a community for twins of all types, ages, and ethnicities in order to provide educational, emotional, and social support through construction of a social network.• to encourage funding for medical and social research relating to multiple births.• to build services to cater to twins' needs by working with researchers, professionals, NGOs, and governmental bodies.• to support families of young twins in order to ease the problems with raising twins or higher order multiples. Recruitment StrategyTo recruit twins a poster and a pamphlet were published inviting all twins to register. These materials were sent to all public and private hospitals, clinics, secondary schools and high schools, colleges and universities, ministries, public offices, and shopping centers. The information was disseminated through mass media such as radio and newspapers. A website was created to maintain the recruitment process as other sources of advertisement proved to be costly. The recruitment process is slow but ongoing. We will translate the website to other languages (Malay, Chinese, and Tamil) to involve more twins. Advertisements in health section of local newspapers have shown to be efficient and will be continued. Zygosity DeterminationTwin zygosity is determined from twins' or their parents' responses to a zygosity questionnaire that inc...