A study of anisotropic magnetoresistance (MR) has shown that the addition of Ir to Ni, Co, Fe, Fe.2Ni.8and Co.3Ni.7crystalline films causes a negative MR. These negative values occur at room temperature as well as at low temperatures. The MR as defined by , where the ∥ and refer to the direction of magnetization relative to the electrical measuring current, can have values cm in Co-Ir. At Ir content of 3% the ratio is -2.6%. Comparisons are made with other alloy systems, and the implication of negative values of on theoretical models is considered.