Eighteen monkeys, trained to perform auditory and visual discrimination avoidance tasks, were exposed to reflected shock tube air blast of 30, 40, or 50 psi. Results indicated that: (1) immediate but transient perfomance decrement occurred; (2) latency was more affected than accuracy, particularly for the 50-psi group; (3) performance decrement was mild and recovery time brief (usually under 4 hours) despite frank physical injuries; and (4) auditory discrimination underwent more decrement than visual, with eardrum injury occurring frequently.