Even though the .40 S and W is too new to have a large number of actual shootings from which to measure street performance, future performance can be accurately predicted with regression analysis. Twenty-four different loads of known street performance in four other police calibers were fired into gelatin to correlate street performance with gelatin performance. These proven loads were equally divided between ones with good, fair, and poor street records. The four characteristics recorded in gelatin from these established loads were penetration depth, recovered diameter, permanent crush cavity, and temporary-stretch cavity. Each bullet characteristic in gelatin was plotted against its known street performance for every load. The tests produced a set of simple formulas that predict future performance based on past performance. All loads that work the same in gelatin will work the same on the street. All of the new .40 S and W loads were fired into gelatin. The best loads from 9-mm +P+ and .45 Auto have a street effectiveness of 85-89 percent. The best .40 S and W loads are in the 86-92 percent range. Based on this analysis, the best performance from the .40 S and W will come from the 150 to 155 grain hollowpoints, the 180 grain high velocity +P hollowpoints and the 180 grain standard velocity Hydra Shok. A chart shows test results for each brand tested according to heavy hollowpoints, light hollowpoints, and training ammo.