Mucins are complex glycoproteins expressed by glandular epithelia and the carcinoma which develop from these tissues. The core protein is aberrantly glycosylated in cancers, and some antibodies show specificity in their reactions with the cancer-associated mucins, which also contains epitopes recognized by T-cells from pancreatic and breast cancer patients. Based on the PCR amplification of the mucin coding sequences, hybridization analysis and determination of the sequence divergence we present the evidence that mucin coding sequences are conserved in a number of species. A broad series of organisms were examined for analogous sequences. Data show that mucin-type sequences are present in a variety of mammals, but less apparent in chicken and yeast. Divergence increased in the order human, monkey, rabbit/rat/cow, mouse; chicken and yeast exhibited minimal homology. Furthermore, nucleotide sequences not included in the tandem repeats, a common feature of mucin core structure, are more conserved than the flanking sequences which also suggests that the flanking sequences may be functionally significant while repeats are structurally important. The hybridization bands showed different restriction patterns (suggesting for the existence of the restriction fragment length polymorphism). Northern analysis indicates message polydispersity, commonly seen with this class of RNA. The major features of the protein appear broadly conserved in the different mammalian species examined. The evolutionary significance of the above studies has been discussed.