The variation of the radiation emitted by a patient, who had been treated with a small quantity of J-131 against hyperthyroid, was followed with a Geigercounter over a period of about two months. The daily measurements were performed at a distance of 6 cm from the neck of the patient at a given time during the afternoon.The following results were obtained from the measurements: a) The first 11 days an anomalous emission of radiation was recorded. b) The next 3 weeks, the emitted radiation reduced to 1/3 of its biggest initial value, with only small fluctuations. c) In the following period of time the radiation reduced further to 1/12 of its initial value, with a reducing tendency and approaching the natural environmental emission values. Especially during the first days after treatment, the behavior of the emitted radiation of radioactive iodine from the patient as described above, did not follow the expected pattern of radioactive decay, which would correspond to a half-life period of 8 days. The irregular behavior mentioned and its possible sideeffects on a suspected developing cancer on the left breast of the patient are due to be discussed in this work.