We analyze 3,547 initial public offerings (IPOs) from 1985 through 2003 to determine the impact of acquisition activity on long-run stock performance. The results show that IPOs that acquire within a year of going public significantly underperform for 1- through 5-year holding periods following the 1st year, whereas nonacquiring IPOs do not significantly underperform over these time frames. For example, the mean 3-year style-adjusted abnormal return is – 15.6% for acquirers and 5.9% for nonacquirers. Our cross-sectional and calendar-time results suggest that the acquisition activity of newly public firms plays an important and previously unrecognized role in the long-run underperformance of IPOs.