14 were found in the exposed Marshallese (none over 1%). The hematocrit values showed a tendency toward anemia in both the exposed and unexposed groups (Table 6). The males >15 years of age showed the greatest difference with a mean hematocrit of 38.7, which was 5.6% below the unexposed mean for this age group. There were 53% of the exposed and 46% of the unexposed people who had hematocrits of less than 37. As with the leukocytes, there was a drop in the hematocrit levels (5 to 10%) compared with the two-yearlevel. Reticulocyte counts. In the exposed group 15.7% showedreticulocyte counts of 3% or more. In the unexposed group 24.4% had values this high. In the Utirik group 64% had values of 3% or more. In no case were reticulocytes greater than 5% observed. Sickling tests showed nosickling tendency in any of the people. Blood groups. Examination of 137 blood samples from the Rongelap people (exposed and unexposed) showed the following: blood group O, 59%; A, 20%; B, 16%; and AB, 5%. Thedistribution of these groups was about the samein the exposed and unexposed people. All blood samples examined were Rh positive. There were no “V” groups characteristic of the Negroid race.** The distribution of these blood groupsis similar to that seen in the Asiatic races.* Bone marrow smears on four irradiated and four unirradiated people showed no abnormalities or deficiencies of cellular elements. Counts in the Atlingnae group. As can be seen from Table 6, the 18 Ailingnae people showed a blood picture similar to that of the other exposed Rongelap people. WBCandneutrophils were as high as in the unexposed groups with slightly lower lymphocyte levels. The platelets in the males (but not in the females) wereslightly below the unexposed level. The mean hematocrit values were slightly higher than in other exposed Rongelapese and about the sameas in the unexposed group. This group also showed the same depression of leukocytes compared with last year’s levels. Counts in the Uturik group. It is apparent from Table 6 that the peripheral blood elementsin the *Weare most grateful to Dr. Amos Cohan, Director, Knicker- bocker Foundation, Inc., New York City, for carrying out the blood group studies. Utirik people were as high as or, in most cases, higher than the unexposed Rongelap level. This group is in fact more comparable with the twoyear Rita control group. Immune response: Primary and secondary tetanus antttoxin production. The data shown in Table 7 are expressed in international units of tetanus toxin neutralized by 1 ml serum. The averagetiter of the irradiated group was aboutthreetimesless than the average titer obtained from the unirradiated group. However,the irradiated group had 25% greater response to the second stimulus than did the unirradiated group. Statistical analysis indicated that the difference in either case was not significant.* Blood chemistry: Proteins. Total serum proteinsas measuredbyspecific gravity and refractometer showed unexpectedly high levels in both exposed and unexposed groups. There wasno difference in total protein or electrophoretic pattern of proteins between the exposed and the unexposed people. The meantotal serum proteins for the pooled groups are presented below: Group METHOD (sp. GR.) FALLING DROP PROTEINOMETER Exposed Rongelap Unexposed Rongelap Utirik 1.0303 1.0312 1.0294 7.99 8.36 7.67 (GMS prorein) Blood proteins of the sera from 37 people (19 exposed and 18 unexposed) examined electrophoretically showed the following mean distribution of albumin and thevarious globulin groups (expressed in gramsbasedonthetotal proteins): ** GLOBULIN ALBUMIN ALPHA]! Marshallese Normal (American) 3.9 4.2-4.6 ALPHA BETA 0.27 0.6 1.0 0.18-0.27 0.4-0.6 0.7-0.9 It can be seen that the increase in proteinsis largely due to the gamma globulin fraction. Figure 16 is a representative pattern of one of the Marshallese with a normal American pattern superimposed. *Weare grateful to Dr. R.D. Stoner of Brookhaven National Laboratory for carrying out the serum titer determinations. **We are indebted to Lt. D.R. Davis (MSC) USNofthe Naval Medical School for the electrophoretic analyses.