A new experiment, AD-4/ACE (antiproton cell experiment), has been approved by the CERN Research Board. The experiment is scheduled to begin taking data in June and continue through the 2003 run cycle. The experiment is designed to determine whether or not the densely ionizing particles emanating from the annihilation of antiprotons produce an increase in "biological dose" in the vicinity of the narrow Bragg peak for antiprotons compared to protons. This experiment is the first direct measurement of the biological effects of antiproton annihilation. The background, description, and status of the experiment are given.