Human placental chorionic villar extracellular matrix derived from villar fragments fractionated according to size on 153, 210, 250 and 300 micron mesh opening nylon sieves was subjected to extraction by acetic acid and denaturing solvents under reducing and non-reducing conditions. Extracellular matrix derived from the smallest villar fragments (153 fraction) was most readily soluble in either acetic acid, guanidine thiocyanate or urea in the absence of reducing agents, while that derived from the largest villar fragments (300 fraction) was least soluble in these agents. Conversely, subsequent extraction, under reducing conditions, of the residues remaining after initial treatment with 6 M urea or 4 M guanidine thiocyanate alone, solubilized more material from the 300 fractions than the 153 fractions. From 25-40% of the matrix was not soluble in denaturing solvents even in the presence of reducing agents with that derived from the largest villar fragments being least soluble. While the chemical composition of the three fractions derived from urea extraction of villar extracellular matrix all contained collagenous components, the non-reduced extract was less collagenous than the matrix itself, while the reduced extract was more collagenous. The insoluble residue remaining after complete extraction was most collagenous and contained the highest content of galactose and glucose indicating that it was probably richest in collagenous components of basement membrane origin. Both the unreduced and reduced urea extracts derived from the four different villar sieve fractions had similar amino acid and carbohydrate compositions and gave identical gel electrophoretic patterns under both nonreduced and reduced conditions indicating the similarity of the extracellular matrix materials derived from different size villar fragments. The data support the multicomponent nature of the placental villar extracellular matrix which appears to consist of a mixture of collagenous and non-collagenous components associated by noncovalent forces and reducible disulfide and nonreducible covalent cross-linkages.