[en] This paper describes efforts to develop microscale methods for mechanical testing of radiation damaged metals. The objective of this program is to simulate fast neutron damage in cladding steels using high energy, heavy ions. While these ion beams can create large levels of radiation damage, e.g. 100 displacements per atom, they do so over a limited depth from the surface of the sample, on the order of several microns. Recent work by Hosemann et al. introduced the concept of applying the micropillar compression approach to irradiated metals to assess their mechanical properties. Building on this work, the current paper examines the fundamental issues of accuracy and precision of the micropillar approach by using copper single crystals with several levels of irradiation damage and many pillars per condition. The result is that we can accurately model and assess the changes in the mechanical behavior of the copper as a function of radiation damage. Copper single crystals of <110> and <111> orientations were irradiated using 20MeV copper ions at nominally room temperature until a damage levels of 50dpa and 100dpa had been achieved. Micropillars of 5μm in diameter and 10μm in height were fabricated from these samples using a 30keV gallium ion beam on a FEI dual-beam focused ion beam (FIB) machine. Compression testing was performed in feedback displacement control using a Hysitron Performech Triboscope nanoindentation machine with a diamond, flat punch of 25μm in diameter. As shown, there are two distinct bands of stress strain curves; distinguishing the control samples (no irradiation) from the irradiated (100dpa) samples. Even, so there is no distinct difference in initial yield point between the two populations with many, visible displacement jumps discernable for both conditions. There is a marked increase in the work hardening rate for the irradiated material. The level of scatter in the data appears to be greater for the irradiated material. The SEM micrographs explain these observations and underscore the need for careful development of the micropillar approach prior to application to complex microstructures. Slip bands are observed throughout the volume of the micropillar as would be expected. These distinct slip bands mostly likely correspond to the observed jumps in strain (displacement) shown. Sslip bands are only observed in the lower half of the micropillar as shown. The upper half of the pillar has been hardened by irradiation so that no slip is possible under the current loading conditions. The lower half, however, has several, discrete slip bands as observed in the control pillar. We are currently performing micropillar compression tests on a series of pillars of different sizes to force the deformation into the irradiated zone nearer to the surface. We will discuss the optimization of this approach and its application to cladding steels