As part of a wider archeometallurgical investigation the present paper records the results of mechanical tests on iron-phosphorus alloys, which were important in early iron usage. Phosphorus increases the yield and ultimate tensile strengths with a corresponding reduction in ductilities as measured by elongation and reduction in area, to a point where brittle failure occurs. However, the work hardening exponent is only slightly decreased and some cold working, as in drawing, can be achieved. The presence of carbon complicated these effects.