A shadow shield whole body counter with automated gamma spectrum analysis is used in the division of nuclear medicine for the measurement of whole body radioactivity. After the radioactive fall-out in Austria caused by the Chernobyl accident the instrument has been extensively utilized for the assessment of the radiation level in the general population. In November of 1986 and 1987 the level of internal contamination with 137Cs in high-performance athletes was compared with a group of subjects practicing little or no sports. It was found that significantly higher contents of 137Cs were present in the athletes. Furthermore, it was found that within the groups of athletes male subjects had significantly higher internal 137Cs contamination per kilogram of body mass than the female subjects. An explanation for this is the different nutrition and the higher relative muscle mass of the athletes.