Lead level data collected from ongoing sequential tap sampling conducted by the Boston Water and Sewer Commission (BWSC) provides information on the impact that lead service line replacement (LSLR) may have on lead levels measured at the tap. Samples were collected before, during and after replacement of the homeowner's lead service line section at two sites where the BWSC had previously replaced the utility-owned portion of the lead service. Results at one site indicated that lead levels may be high immediately after LSLR, and for up to 2 days after, due to the presence of particulate lead, but were reduced to low levels by 2 months after replacement. Results at another site indicated that lead levels were reduced to approximately detection level within one day of lead service line replacement. Includes tables, figures.