Many high‐field superconducting systems make use of copper as part of the conductor configuration. Copper is present primarily because it combines low resistance with moderately high strength. As copper is exposed to high transverse magnetic fields its resistance increases. This resistance increase, or magnetoresistance, has been experimentally measured for several different grades and tempers of commercially available copper at 4.2°K and in the field range from 0 to 100 000 G. Zero field‐resistance ratios varied from 60 to 1200 due to differing degrees of purity and amounts of cold work. The results of these measurements fit a normalized equation of the type which gives the fractional change in resistance as a function of transverse field and zero field‐resistance ratio. The mechanical properties for these samples have been measured at room temperature and 4.2°K and the yield stress correlated with the resistance properties.