Measurement of gamma-ray activity was made on 520 men's watches, 51 ladies' watches, 120 boys' watches, and 66 girls' watches and the respective average radium contents obtained were: 0·059, 0·035, 0·031 and 0·017 μg. The frequency of persons wearing luminous wrist watches was estimated from a total of 1436 adults and children. The genetically significant dose to the Danish population has been calculated and found to be approximately 1·2±0·4% of that from the natural background.