Summary: Transmitted resistance to antiretroviral drugs in acute and early HIV-1 infection has been well documented, although overall trends vary depending on geography and cohort characteristics. To describe the changing pattern of transmitted drug-resistant HIV-1 in a well-defined cohort in New York City, a total of 361 patients with acute or recent HIV-1 infection were prospectively studied over a decade (1995-2004) with respect to HIV-1 genotypes and longitudinal T-cell subsets and HIV-1 RNA levels. The prevalence of overall transmitted resistance changed from 13.2% to 24.1% (P = 0.11) during the periods 1995 to 1998 and 2003 to 2004. Nonnucleoside reverse transcriptase inhibitor resistance prevalence increased significantly from 2.6% to 13.4% (P = 0.007) during the same periods, whereas prevalence of multidrug-resistant virus shifted from 2.6% to 9.8% (P = 0.07) but did not achieve statistical significance. A comparable immunologic and virologic response of appropriately treated individuals was observed regardless of viral drug susceptibility status, suggesting that initial combination therapy guided by baseline resistance testing in the case of acute and early infection may result in a favorable treatment response even in the case of a drug-resistant virus. These data have important implications for selection of empiric first-line regimens for treatment of acutely infected antiretroviral-naive individuals and reinforce the need for baseline resistance testing in acute and early HIV-1 infection.