Nearly all twin registers are based in developed countries and there is no twin register in the devel opi ng w or l d. Our objecti ves w er e to i ni ti ate the pr ocess of establ i shi ng a nati onw i de tw i n register in Sri Lanka by starting a volunteer register first and working towards a population-based r egi ster. Regul ar new spaper adver ti sements, featur e ar ti cl es, r adi o tal k s, and tel evi si on pr ogr ammes w er e used to publ i ci se a competi ti on for tw i ns, thei r par

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... ents/r el ati ves and fr i ends r equesti ng them to par ti ci pate by sendi ng i n detai l s of tw i ns. The competi ti on r an fr om 28 M ar ch 1997 for a per i od of 3 months. I t offer ed pr i zes for thr ee w i nner s sel ected by dr aw i ng l ots. A dver ti sements hi ghl i ghted the objecti ve of the competi ti on as establ i shi ng a tw i n r egi ster for futur e r esear ch and emphasi sed that i nfor med consent w oul d be obtai ned for i ndi vi dual r esear ch pr ojects. Those w ho r egi ster ed compr i se 4602 tw i n pai r s (same sex: mal e -1564, femal e -1885; di ffer ent sex -1153), 80 sets of tr i pl ets (same sex: mal e -17, femal e -31; di ffer ent sex -42) and tw o sets of quadr upl ets (di ffer ent sex). The ol dest tw i ns, tr i pl ets, quadr upl ets ar e 85, 46, and 5 year s ol d, r especti vel y; 88.0% of tw i ns ar e l ess than 30 year s ol d. A l though other s have pr evi ousl y used media publicity to enrol twins in twin registers, we believe this to be the first time that twins have been enr ol l ed thr ough competi ti on. We have mor e young tw i ns, and our gender and zygosi ty pr opor ti ons after appl yi ng Wei nbur g's r ul e do not match the pr opor ti ons expected fr om a vol unteer tw i n sampl e. Establ i shi ng a tw i n r egi ster for r esear ch pur poses has pr oved possi bl e i n a devel opi ng countr y. Twin Research (2000) 3, 202-204. Keyw or ds: vol unteer regi ster, competi ti on for tw i ns, new spaper adverti sements, Wei nberg di fferenti al method Correspondence: A Sumathi pal a, Secti on of Epi demi ol ogy and General Practi ce, Insti tute of Psychi atry, Ki ngs Col l ege,