The paper describes an accidental 137Cs internal and external contamination of a woman 28 years old by handling of two unsealed 137Cs sources of 2.5 Ci total activity. The only abnormality found by laboratory tests was leukopenia. The chromosomes of blood lymphocytes were also investigated. 137Cs content in urine between the 8th and 40th day after accident ranged from 34, 53 to 12.01 nCi/day. The mean feces: urine ratio was 0.25 +/- 0.06. The increase of 137Cs excretion in urine, after administration of diurectic "Lasix" and potassium was not observed. Mean biological half-life calculated from regression curve was 64 days. Body content found by whole body counting, performed on the 8th and 15th day after accident, was 6.5 muCi and 5.1 muCi respectively. The initial 137Cs body burden of 6.9 muCi was calculated for the value 5.1 muCi. The corresponding total radiation dose was 0.26 rads and quarterly dose was 0.16 rads.