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.