In recent years there has been a great deal of interest in the measurement of DNA hybridization at surfaces. Surface-confined DNA hybridization has been used to monitor gene expression, to detect the presence of a particular DNA sequence and determine single nucleotide polymorphisms (SNPs). DNA microarrays, which can contain thousands of discrete DNA sequences on a single surface, have become widely used for hybridization studies. While a powerful technique, this technology is limited by the stability of the fluorescent dyes used to label the DNA, and the need to perform measurements ex-situ to reduce the fluorescence background. In this report, we describe the use of colloid-amplified surface plasmon resonance (SPR) to measure DNA hybridization at surfaces. SPR is a surface sensitive technique, which can be used to study hybridization in situ, and the use of colloidal metal tags provides excellent sensitivity. Angle-scanning SPR has been used to study oligonucleotide hybridization to surface confined probes, and work is underway to apply SPR imaging to study DNA hybridization in macro- and microarray formats.