We characterize the microstructure of the market for Treasury inflation-protected securities (TIPS) using novel tick data from the interdealer market. We find a marked difference in trading activity between on-the-run and off-the-run securities, as in the nominal Treasury securities market. We find little difference in bid-ask spreads or quoted depth between on-the-run and off-the-run securities, in contrast to the nominal market, but we do find a sharp difference in the incidence of posted quotes. Intraday activity differs strikingly from the nominal market, with activity peaking in the mid-to-late morning. Announcement effects also differ from the nominal market, with auction results and consumer price index announcements eliciting particularly sharp increases in trading activity.