The project compared adverse event reporting rates for Lederle's DTP and DTPH vaccines. Fourteen lots of DTPH vaccines and 14 contemporaneous lots of DTP were selected. Adverse Event REports (VAERS reports) reporting rates were calculated for 20 categories of adverse events, including the categories of all serious and death events. Significant elevations of reporting rates for DTPH vaccine were found for many categories of events including all events and serious events. "Relative risks" were between 1.5 and 2.5 (DTPH/DTP) and p values ranged down to 10-4.