A novel approach to the measurement of arsenic and selenium in nail phantoms is demonstrated. Two-component nail phantoms of 0.7 mm and 1.5 mm thickness were made from a polyester resin-salt mixture and dosed with equal arsenic and selenium concentrations ranging from 0 to 30 microg g(-1). A backing was made to simulate the soft tissue and bone of the great toe. Characteristic x-rays for arsenic and selenium were recorded using a portable x-ray tube and a silicon PiN diode detector. The minimum instrumental detection limits for arsenic and selenium in 0.7 mm solitary nail samples were as follows: 0.510 +/- 0.018 microg g(-1) and 0.519 +/- 0.026 microg g(-1) respectively; for 1.5 mm solitary nail: 0.465 +/- 0.035 microg g(-1) and 0.561 +/- 0.062 microg g(-1); for 0.7 mm nail with backing: 1.522 +/- 0.038 microg g(-1) and 1.401 +/- 0.049 microg g(-1); for 1.5 mm nail with backing: 1.354 +/- 0.054 microg g(-1) and 1.367 +/- 0.068 microg g(-1).