-2Marshall Islands, plus a matched control population consisting primarily of unexposed Rongelap people, In addition, a limited surveillance has been provided to those persons who were relocated from Bikini. The approximate numbers of Marshallese are: Rongelap ~ 90 Utirik ~~ 160 Matched controls -~ 200 Bikinians ~ 140 TOTAL ~~ 590 Depending upon circumstances, usually three of four trips are made each year to these locations, Brookhaven National Laboratory (BNL) Medical Department physicians coordinate and direct these programs, One of these trips consists of a large medical staff (usually 12), the majority of whom are specialists from various leading U.S, medical centers and institutions, At this time the annual physical examinations are given, including hematological, urological, serological and other examinations as appropriate, During these visits, "sick call'' is held for all residents wishing medical attention; this usually results in up to several hundred persons on each atoll seeing the physicians. Included in "sick calls" are physical examinations, blood tests, treatment if possible, and referral to the Trust Territory Health Services, f Other visits during the year are far more specialized examinations (e,g., pediatrics, thyroid, dental, intestinal parasites, etc,) and include BNL staff and appropriate specialists.