The aims of this study were thus to: 1) assess the effect of endogenous degradation on elasticity of CF sputum; 2) assess the effect of depolymerization of DNA and mucins on elasticity; 3) quantify the levels of airway mucins MUC5AC and MUC5B in CF sputum; and 4) assess the effects of degradation of MUC5AC and MUC5B on apparent mucin concentrations. Here, MUC5B is linked to cystic fibrosis.