Experiments were conducted in Mississippi in 1986 and 1987 to enumerate populations of total and Gram-negative bacteria on cotton lint from boll opening through harvest. The influence of environmental conditions and cultural practices on these populations was also monitored. Results of these studies indicated that populations of total and Gram-negative bacteria increased rapidly after boll opening. Populations generally increased in response to moisture and an application of a defoliant. The most common genera found were Acinetobacter sp., Bacillus sp., Enterobacter sp., Flavobacterium sp., and Pseudomonas Sp.