Native type Ⅳ collagen (CⅣ) was isolated and purified from human placenta by pepsin limited digestion, fractional salt precipitation, reduction and alkylation, and cellulose chromatography. The two constituent α peptide chains of the purified CⅣ were identified by SDS-PAGE. Antiserum was prepared by immunizing rabbits with the purified CⅣ. The obtained antiserum against human CⅣ showed high titer and specificity.