Lactobacilli have long been considered to be the protective flora in the vagina. Women with vaginal infections have used various non-prescription products in an attempt to restore their normal vaginal flora. Products that contain lactobacilli include dairy products (yogurt, acidophilus milk) and commercially available Lactobacillus powders and tablets. Recently, Lactobacillus species that produce hydrogen peroxide (H2O2) have been associated with normal vaginal flora. In this study, we compared 16 non-prescription products containing lactobacilli for H2O2 production, purity, and identifiable contaminants. All 16 products contained lactobacilli, of which ten (62%) produced H2O2. At least one contaminant was detected in 11 of 16 (69%) of the products: Enterococcus faecium (ten), Clostridium sporogenes (one), Streptococcus mitis (one), and Pseudomonas species (one). Although all of the products tested contained lactobacilli, only four of the products contained Lactobacillus acidophilus. Most of the lactobacilli-containing products currently available either do not contain the Lactobacillus species advertised and/or contain other bacteria of questionable benefit. We conclude that commercially available products may not be appropriate for recolonization of the vagina.