Human alpha defensins 1, 2, and 3 are produced by CD8 T cells of HIV-infected long-term nonprogressors and have an antiviral activity. alpha Defensins were examined in peripheral blood mononuclear cells (PBMCs), cervical-vaginal mononuclear cells (CVMCs), and cervical biopsies of 9 HIV-1-exposed but uninfected women (ESNs), 10 HIV-infected patients (HIV), and 13 low-risk healthy controls (HCs). Results showed that, whereas alpha defensin production and alpha defensin-expressing CD8 lymphocytes were comparable in ESNs and HIV patients, constitutive alpha defensin production by peripheral CD8 and CVMCs was augmented in ESNs compared with HCs (P = 0.001 and P = 0.058, respectively); alpha defensin mRNA was increased in PBMCs of ESNs; unstimulated, alpha defensin-expressing peripheral and mucosal CD8 lymphocytes were 10-fold higher in ESNs compared with HCs (P = 0.003 and P = 0.01, respectively); and alpha defensin mRNA and alpha defensin-expressing cells were augmented in cervical biopsies of ESN compared with HCs (mRNA:P = 0.03). The differences were reduced upon in vitro mitogen stimulation. A robust constitutive production of alpha defensin is seen in HIV-exposed uninfected individuals; these peptides could have a role in the potentially protective immune response that characterizes ESNs.