The utility of the inert gas shielded nitrous oxide-acetylene flame for the determination of arsenic and selenium by atomic absorption spectrometry has been demonstrated elsewhere1. The low background absorbance of the fuel-rich, 50 mm path-length flame (ca4 and 5% at the As 193.7 and Se 196.0 nm lines respectively) permits the attainment of detection limits which are equal to, or somewhat superior to, those obtainable with the air-acetylene flame. The AAS sensitivity (that concentration producing 1% absorption), however, is decreased; this is the result of the shorter path length of this flame compared to that employed for air-acetylene (100 mm) and the lower concentration of analyte produced in the larger volume of gas used to support the flame.