[en] Skin tissues were collected from 8 A-bomb survivors and 4 non-exposed controls. Chromosome analysis among the non-exposed persons revealed normal karyotypes in all sites, including one cicatricial site. Structural chromosome aberrations were observed in 5 exposed persons (19 %, 76 %, 10 %, 5 %, and 2 %, respectively, of analyzable cells), all of whom had presented with acute symptoms after the bombing. In two survivors exposed at 1,250 m and at 1,390 m from ground zero, abnormal clones were detected in the cells from cicatricial site tissues, and in those from normal site tissues as well in one of them. An analysis for phytohemagglutin-stimulated peripheral lymphocytes performed in these survivors revealed chromosome aberrations in 19 % and 12 %, respectively. (Namekawa, K.)