Composite nonlinear optical materials consisting of silver nanoparticles, approximately 11 nm in diameter, in a polymer host were prepared. The polymer used in the preparation of the composites was a polyurethane bearing a tricyanovinyl moiety. The composite preparation method and polymer pretreatment method as well as pretreatment of the silver colloids to control particle agglomeration are described. The (chi) (3)xxxx of a composite was measured by degenerate four-wave mixing as 3.65 X 10-10 (esu), 7.91 X 10-11 (esu) and 5.86 X 10-11 (esu) at 532 nm, 562 nm, and 570 nm, respectively. The interfacial chemical interactions between the silver colloid and polymer host in the composites were explored using Raman, infrared, UV- visible, and NMR spectroscopy.