 The mechanical properties of porcine brain tissue were investigated when subjected to strains up to 70% at strain rates between 1 and 50 seconds 1. It was found that the tissue exhibits stiffness increases with increasing strain rate, with the highest stiffness observed at a strain rate of 50 seconds 1. Additionally, the stress relaxation behavior of the tissue was studied using a combination of time and strain domain analysis. It was found that the stress relaxation can be described by a product of two mutually independent functions of time and strain, with the peak stress being proportional to the square root of the strain rate. This reduced stress relaxation function can then be used to predict the mechanical behavior of brain tissue in compression with strain rates greater than 10 seconds 1. This article was authored by Azataka Tamura, Sadayuki Hayashi, Aisawa Watanabe, and others.