Abstract: A method for the rapid estimation of hyperplastic and hypertrophic changes in animal airways is an assay which specifically measures acidic and neutral mucoproteins in a linear fashion from 0.5 to at least 10 .mu.g. The assay comprises exposure of a test animal to a suspected metaplastic inducer, removal of the lungs, homogenization in an appropriately buffered solution containing reducing agents and protease inhibitors; removal of particulate matter; and size-fractionation of the SDS treated soluble extract. The high molecular weight material is immobilized and stained for either acidic or neutral mucosubstances and the specific staining is quantitated. The changes observed are consistent with those seen in histological sections of the exposed tissues.