The 2008-09 season onset for all 10 HHS regions, excluding Florida, ranged from mid-October (week ending October 11, 2008) to late-December (week ending December 27, 2008) (Table and Figure). The season onset for Florida was the week ending July 12, 2008 and continued until the week ending February 7, 2009. The 2008-09 season offset for all 10 HHS regions and Florida ranged from early February (week ending February 7, 2008) to mid-April (week ending April 11, 2009) (Table and Figure). Excluding Florida, the median season duration among the 10 HHS regions was 16 weeks (range: 14-23 weeks). The region with the shortest season was Region 3 (Philadelphia region) (14 weeks), and the longest season was in Region 4 (Atlanta region) (23 weeks). Preliminary data for the current 2009-10 RSV season (week ending July 28, 2009–February 20, 2010) were reported by 634 laboratories from all 50 states and the District of Columbia. A total of 316,453 RSV antigen detection tests were performed, and 50,070, (16%) positive results were reported to NREVSS. The season onset had occurred in all 10 HHS regions by February 20, 2010. Nationally, the 2009-10 RSV season onset occurred during the week ending November 14, 2009; however, when data from Florida were excluded, the national season onset occurred 1 week later (week ending November 21, 2009). Weekly updates showing RSV national, regional, and state trends are available from the NREVSS website at http://www.cdc.gov/surveillance/nrevss. Additional information about Florida RSV trends is available from the Florida Department of Health website at http://www.doh.state.fl.us/disease_ctrl/epi/rsv/rsv.htm.