Changes between the main types of mucins in the goblet cells and colonic microbiota in obese rats were studied. Paraffin histological slides of the colon of control and obese rats were stained with periodic Schiff (to visualize all mucins in the goblet cells), alcian blue with pH 2.5 (to visualize acidic mucins), aldehyde fuschin (to visualize sulphomucins), alcian blue and periodic Schiff (to distinguish between neutral and acidic mucins), alcian blue and aldehyde fuschin (to distinguish between sialo- and sulphomucins). Also, the composition of microbiota in feces was determined on selective and differential media. It has been shown, that obesity is accompanied by hypoplasia and hypertrophy of goblet cells in the crypts of the colon. The decrease in the total number of goblet cells in obese animals occurs due to cells producing mixed mucins with a predominance of acidic mucins, as well as cells producing sulphomucins or mixed sulphomucins and sialomucins. As result, the percentage of goblet cells producing neutral, mixed neutral-acidic or sialomucins increases. The percentage of cells producing acidic-neutral mucins, sulfomucins or mixed sialo- and sulfomucins decreases. At the same time, the number of Bifidobacterium and lactose-fermenting E. coli (sucrolytic bacteria) decreases in feces. The number of mannitol-negative staphylococci (transient microbiota) increases. The number of Clostridium, Staphylococcus aureus and yeast-like fungi Candida does not change.