The present invention provides a new class of Raman-active reagents for use in biological and other applications, as well as methods and kits for their use and manufacture. Each reagent includes a Raman-active reporter molecule, a binding molecule, and a surface enhancing particle capable of causing surface enhanced Raman scattering (SERS). The Raman-active reporter molecule and the binding molecule are affixed to the particle to give both a strong SERS signal and to provide biological functionality, i.e. antigen or drug recognition. The Raman-active reagents can function as an alternative to fluorescence-labeled reagents, with advantages in detection including signal stability, sensitivity, and the ability to simultaneously detect several biological materials. The Raman-active reagents also have a wide range of applications, especially in clinical fields (e.g., immunoassays, imaging, and drug screening).