Surface Plasmon Enhanced Fluorescence Spectroscopy (SPFS) has been used to monitor the hybridization reaction of fluorophore-labeled 15mer target oligonucleotides from solution to probe DNA previously immobilized on plasma-polymerized allylamine films (ppA). The surfaces were treated with 254 nm UV light to covalently link the probe DNA to the ppA films. Since strong unspecific adsorption would occur between target DNA and unreacted amino groups on the polymer surface, any remaining reactive moieties in the polymer film were neutralized by rinsing the substrate surface with succinic anhydride after probe adsorption and before target hybridization. The SPFS data were utilized to determine hybridization affinity constants (K-A) for complementary targets (MM0) as well as mismatch 1 (MM1) and mismatch 2 (MM2) hybridization reactions. Complementary target (MM0) DNA hybridization was shown to have a significantly higher K-A than that MM1 and MM2. The three-dimensional network of the ppA appears to allow a similar hybridization mechanism in comparison to the more conventional two-dimensional systems.