UNLABELLED As annual influenza epidemics continue to cause significant morbidity and economic burden, an understanding of viral persistence and transmission is critical for public health officials and health care workers to better protect patients and their family members from infection. The infectivity and persistence of two influenza A (H1N1) virus strains (A/New Caledonia/20/1999 and A/Brisbane/59/2007) on stainless steel (SS) surfaces were evaluated using three different surface matrices (2% fetal bovine serum, 5 mg/ml mucin, and viral medium) under various absolute humidity conditions (4.1 × 10(5) mPa, 6.5 × 10(5) mPa, 7.1 × 10(5) mPa, 11.4 × 10(5) mPa, 11.2 × 10(5) mPa, and 17.9 × 10(5) mPa) for up to 7 days. Influenza A virus was deposited onto SS coupons (7.07 cm(2)) and recovered by agitation and sonication in viral medium. Viral persistence was quantified using a tissue culture-based enzyme-linked immunosorbent assay (ELISA) to determine the median (50%) tissue culture infective dose (TCID50) of infectious virus per coupon. Overall, both strains of influenza A virus remained infectious on SS coupons, with an approximate 2 log10 loss over 7 days. Factors that influenced viral persistence included absolute humidity, strain-absolute humidity interaction, and time (P ≤ 0.01). Further studies on the transfer of influenza A virus from fomites by hand and the impact of inanimate surface contamination on transmission should be performed, as this study demonstrates prolonged persistence on nonporous surfaces. IMPORTANCE This study tested the ability of two influenza A (H1N1) virus strains to persist and remain infectious on stainless steel surfaces under various environmental conditions. It demonstrated that influenza A (H1N1) viruses can persist and remain infectious on stainless steel surfaces for 7 days. Additional studies should be conducted to assess the role played by contaminated surfaces in the transmission of influenza A virus.