The selenium concentration of enamel from samples of human teeth was determined by a method of neutron activation analysis. The samples, weighing approximately 100 mg were irradiated in a reactor at a thermal neutron flux of 1.2 × 1012 n/cm2/sec for 1 hour for 81Se and for one week for 75Se. The selenium activity was measured after radiochemical separation. The samples analysed were obtained in Manchester and in Edinburgh. The mean level of selenium found in the teeth from Edinburgh was 0.830 ppm and the range 0.213–1.96 ppm. In the teeth from Manchester the mean level was 0.914 ppm and the range from 0.274 ppm–2.08