RATIONALE. HIV infection results in alterations to the intestinal tract, even in clinically healthy patients. Changes may include pronounced CD4 T-cell loss, enteric nerve and smooth muscle degeneration, abnormal enterocyte morphology, altered gene expression patterns, increased intestinal permeability, and decreased absorptive capacity. Recently it was found that HIV infection may also result in abnormal low-level leakage of lipopolysaccharide (LPS, a gram-negative bacterial product) from the gut into the circulation which promotes systemic immune activation. As immune activation is a strong positive correlate of HIV disease progression, it may be very important to develop effective means to improve intestinal barrier function in HIV infection. Evidence also exists that uninfected individuals of African descent may have higher intestinal permeability than uninfected Caucasians, suggesting that intestinal dysfunction in the event of HIV infection could differ between the two races. With regard to gender, women have been shown to display more pronounced inflammatory responses to LPS compared to men. Intriguing research outside the HIV field using animal models of compromised gut barrier function and also using human subjects with trauma- or disease-associated intestinal leakage has shown that oral administration of certain probiotic bacteria can 1) Reduce bacterial translocation, 2) Reduce bacterial infections, 3) Decrease inflammatory cytokines, and 4) Improve survival. Thus, probiotics could offer important benefits to HIV infected patients by improving intestinal function and reducing subsequent microbial translocation and immune activation. These benefits may vary by race.