The effects of environmental factors on the gram negative bacterial (GNB) content of cotton were evaluated. Raw cotton was obtained early in the harvesting season or late in the season after the first killing frost. The samples were separated into senescent bracts, pericarps, green bracts, and leaves. Each part was analyzed for its GNB content. Seed cotton obtained from the green bracts was also analyzed. Raw cotton samples were analyzed for endotoxins. Additionally, green capsules and bracts of a noncommercial genetic cotton stock were artificially frozen by applying a freon aerosol. Ten to 21 days later, the capsules which had opened and the bracts were analyzed for GNB. The highest concentrations of GNB were found in senescent bracts, followed by the pericarps, green bracts, seed cotton, and leaves in that order. Artificially frozen green cotton capsules had a much higher concentration of GNB on both bracts and seed cotton than unfrozen capsules. Raw cotton harvested late in the season contained significantly higher concentrations of GNB and endotoxins than cotton taken early in the season. The authors conclude that environmental variables can have a strong effect on bacterial contamination of cotton.