Silver nanodendrites are synthesized by a simple surfactant-free method using a suspension of zinc microparticles as a heterogeneous reducing agent. Structural characterizations suggest the preferential growth along < 100 > and < 111 > directions by oriented attachment of silver nanocrystals in the diffusion limit, leading to the formation of silver nanodendrites 20-30 nm in stem and branch diameter and 5-50 mu m in length. Surface-enhanced Raman scattering studies show that the silver nanodentrites give an intensive and enhanced Raman scattering when pyridine was used as a probing molecule. We have also demonstrated that the silver nanodendrites increase the sensitivity of an electrochemical glucose biosensor by as much as 1-2 orders of magnitude.