Wyoming montmorillonite has been modified with block copolymers of poly (styrene) (PS) and poly(ethylene oxide) (PEO). Using melt intercalation techniques, PEO-b-PS copolymers spanning a range of volume fractions and molecular weights were mixed with montmorillonite, annealed above the Tg of PS, and characterized using X-ray diffraction. Most of the block copolymers intercalated the clay, with several samples exhibiting multiple Bragg reflections from increased gallery spacing. Samples with higher PEO volume fractions were most likely to have intercalation. For a given PS block length, longer PEO blocks were more likely to produce intercalation. In general, the increased gallery spacings were close to those produced by modifying montmorillonite with PEO homopolymer.