The surface of polycrystalline iron covered by segregated arsenic, phosphorus and sulphur was analysed in a combined electron spectroscopic study by means of Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). The saturation coverage of arsenic at 1033 K was determined as 0.33 +/- 0.02 monolayer. Sulphur, arsenic and phosphorus segregate in competition. A relation giving the surface coverage from the XPS intensity of adsorbed element is deduced from the experiments and is also calculated. Experimental and calculated values are found to be in relatively good agreement.