Conventional Electrical Discharge Machining (EDM) can decrease component fatigue life and strength. Wire-EDM might be less detrimental because the energy input is lower and consequently there is a thinner surface layer modified by the process. The influence of wire-EDM on the S-N fatigue properties of a high strength martensitic stainless steel was investigated. First the effect of four sets of wire-EDM parameters on the surface topography and surface layer thickness was determined. Then one set of parameters was chosen for the fatigue tests, which included reference specimens produced by abrasive jet machining. At stress levels giving fatigue lives less than 10(6) cycles there was no difference in average lives between the reference and wire-EDM specimens. However, the latter showed a significantly lower fatigue strength.