Here we present the first use of intraneural and intrafascicular infrared neural stimulation (INS) with early-generation Utah Slanted Optrode Arrays (USOAs) to produce highly selective, artifact-free stimulation of peripheral nerves. USOAs utilize technology previously developed for Utah Slanted Electrode Arrays, and contain 100 silicon optrodes of 0.5 to 1.5 mm length, spaced 400 μm apart in a 10 x 10 grid. The optrodes penetrate into the nerve and closely abut nerve fibers, thus providing multiple, independent, focal sites of stimulation. We first demonstrated that intraneural (but extrafascicular) infrared (IR) stimulation of cat sciatic nerve with conventional optical fibers coupled to a Lockheed Martin Aculight Capella laser produced stronger and more selective neural and muscle compound action potentials (CAPs) than did extraneural INS. We next tested INS through individual USOA optrodes (e.g., wavelength 1873 nm, 5- ms stimulus pulse, < 1 mJ at optrode tip). In contrast to extraneural INS, intrafascicular INS evoked relatively strong and highly selective, optrode-specific responses. Further, there were no observable stimulus artifacts, thereby allowing adjacent electrical recordings. These initial results indicate that intrafascicular INS via USOAs may provide a more efficient, more selective, high-optrode-count means of activating axons, plus greater access to interior nerve fibers.© (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.