The potential for fretting and corrosion at the taper junction of modular heads and hip stems has been investigated in several laboratory tests. It has been reported that off-axis fatigue testing under acidic (3.5 pH) and at an elevated temperature (50°C) conditions produces fretting and corrosion features observed in some clinical cases. The purpose of the present study was to replicate this extreme condition for some combinations of oxidized Zr-2.5Nb (OxZr), cobalt-chromium (CoCr) and stainless steel (SS) femoral heads with Ti-6Al-4V and SS stem trunnions. After approximately 5 Mcycle of fatigue testing, the contacting surface tapers were inspected using a scanning electron microscope. Amongst the various combinations tested, SS heads coupled with SS trunnions showed more extensive corrosive attack than any other combination. Orange-colored deposits were observed on SS heads tested against SS trunnions. The CoCr heads coupled with Ti-6Al-4V trunnions showed less evidence of corrosive attack, with Cr-rich deposits well away from the engagement point and Ti-rich metal transfer areas near the engagement point. The OxZr heads coupled with either Ti-6Al-4V or SS trunnions showed the least corrosive attack within the junction and produced no signs of visual discoloration. A few localized small Cr-rich areas were observed near the engagement point on OxZr heads coupled with SS trunnions due to selective leaching of iron from the metal transfer area. The fretting performance of any of the couples evaluated in this study under extreme conditions is expected to be at least as good as or better than the SS-SS couples.