A CONVENIENT method for the isolation of bovine submaxillary mucin in a relatively undegraded and homogeneous state compared to earlier methods1 has been developed in this Laboratory. Fresh glands (640 gm.) were ground and stirred mechanically with three changes of 500 ml. of cold water for a total of 54 hr. The pooled extracts were clarified by centrifuging at 26,3600g for 30 min. and adjusted to pH. 3.5. The resulting mucin clot was separated and dissolved in cold water by neutralization to 7.5, and lyophilized. The product was purified by solution in 500 ml. of cold 50 per cent (w/v) aqueous calcium chloride. After centrifugation at 26,360g for 30 min., the supernatant was fractionated with cold ethanol. The fraction separating at 60–75 per cent (v/v) ethanol was collected by centrifugation at 26,360g for 30 min., dissolved in water, dialysed against water and lyophilized. All procedures were carried out at 0–4° C. The yield was 0.64 and 2.5 per cent of the glands on fresh and dry weight basis, respectively. The recovery of sialic acid was 36 and 60 per cent of that in the extract and mucin clot, respectively. A repetition of the procedure did not alter the composition of the product. The lyophilized powder could be stored at 2–4° C. without change of its properties.