Serotype trends amongst multi-drug resistant (MDR) strains obtained from the Canadian Bacterial Surveillance Network between 1993 and 2008 ( n = 11,083). MDR 19F (n = 477), 23F (n = 150), and 6B (n = 221) emerged in the pre- PCV 7 introduction era (before 2001) and continued to rise during vaccine introduction (2002-2005), then declined in post-PCV7 introduction era (2006 onwards). MDR 19A (n = 97) was present in the pre-PCV7 at very low levels and began to rise soon after PCV7 was introduced country-wide. Data for 1999 and 2000 were not collected. Data are presented as the percent of all MDR isolates collected for the given year.