This chapter describes a strategy for the separation and identification of the mucins present in mucous secretions or from cell culture, focusing primarily on those mucins involved in gel formation. At present, the mucins MUC2, MUC5AC, MUC5B, and MUC6 are known to be gel-forming molecules (1–4). These mucins share common features in that they are oligomeric in nature and consist of a variable number of monomers (subunits) linked in an end-to-end fashion via the agency of disulfide bonds. In addition, their polypeptides comprise regions of dense glycosylation interspersed with “naked” cysteine-rich domains (4–7).