12 Impairmentof.hearing was averaged for the two ears as follows: the decibel loss for each of seven combined exposed and unexposed populations; these were plotted, and a curve was drawn accord- 7000) in each ear was averaged to give a mean frequencyloss in decibels for the two ears. Cardiovascular Changes. 1. Systolic and diastolic bloed pressures were obtained with the standard aeronoid cuff-type sphygmomanometer. Two readings were obtained, and the average value the same wayof the 5-year group meansofthe individual mean age scores. The combining of frequencies (200, 500, 1000, 2000, 3000, 4000, and was used. There was no basic or adjusted level of ing to the bestfit by eye. A curve was obtainedin scores into 5-year age groups was done to reduce possible errors due to the uncertainty of the exact age of some individuals. Laboratory Procedures Hematological Examinations. Two complete physical activity such as resting for a standard period prior to the readings. Pressures were taken on the left arm with the subject supine during the course of the physical examination. 2. The degrees of peripheral arteriosclerosis and counts, and Price-Jones curves (for determination The former was estimated by palpation of the peripheralarteries, the latter by viewing the retina with an ophthalmoscope. the electronic Coulter, which proved very satisfactory and time-saving for this type of field examinauon. Differential counts were performed in the routine blood counts were done, about a week apart, and a third was doneon persons showing abnormalities. White blood counts, red blood retinal arteriosclerosis were scored on a 0 to 4+ scale. of red cell size distribution) were obtained with Neuromuscular Function. Neuromuscular function was measured by having the subject depress usual manner after staining with Wright’s fluid. Platelet counts were done by phase microscopy, the key of a hand tallv type of blood cell counter and hemoglobin was determined by the cyan- ute. The total numberof depressions represented eter. Serum proteins were determined with the as many timesas possible in the period of one minthe score. Hand Strength. Hand strength was measured by a Smedley hand dynamometer.* The spring tension ofthe hand grip was measured in kilograms. The maximum squeeze strength in the dominant hand in three tries was recorded. Handling of Date. Becauseof sex differences, some of the above criteria were evaluated sepa- rately for the two sexes; these were baldness, neuromuscular function, and handstrength. In order that the estimated and measured data could be compared and combined,both types of data were converted to a percentagescale. The estimated values 0,1+,2+,3+,and 4+ were presented also as 0, 25, 50, 75, and 100%, respectively. In the case of the measured data, the values associ- ated with least aging were taken as zero percent (sometimes the highest reading, as with hand strength; sometimes the lowest, as with hearing loss), and those indicating most aging as 100%. The data were examined on both an individual basis and a population basis. A mean agescore wasobtained for each individual by averagingall his percenttest values. In studying population trends, means were calculated for each criterion by 5-year age groups (in most cases) including *C.H. Stoelting Company, Chicago,Ill. hemoglobin technique with the Lumitron colonm- Hitachi refractometer. Blood and serum samples for the studies described below were collected in the field, kept under refrigeration, and shipped by air to the various laboratories in the United States for analysis. Urine Analyses. Routine urine analvses were carried out on all people receivingphysical examinations. These included determinationsof protein and hypergiucosuria by reagent paperstrips. * In all cases showing positive findings, the urine was centrifuged and the sediment examined microscopically. In the four cases showing positive urine sugartests, fasting blood specimens were obtained and analyzed for blood sugar at the Naval Dispensary on Kwajalein. Serum Cholesterol. Serum cholesterol was determined in blood samples drawn from exposed and unexposed Rongelap people, and also in about 70 blood samples from people at Utirik Island and 63 from people at Majuro Atoll. These analyses were done at the National Institutes of Health by Dr. J.H. Bragdon and Mr.J.C. Lauter. ComplementFixation Tests. Serum samples ob- tained from 163 exposed and unexposed Rongelap people were frozen and sent to the National Insttutes of Health for various examinations. Com*Clinistix, Ames Company, Inc., Elkhart, Indiana.