Abstract: Viscoelastic hydrogel microparticles are used for repair of tissue defects and injuries or filling and occlusion of anatomical structures. These are administered as a microparticle suspension using a catheter, syringe, steerable catheter tip, or comparable technology into the site, where they can be further stabilized by crosslinking or sealing, or through incorporation of a support or encapsulating structure. Materials and methods for solidifying, stabilizing and sealing these materials can be used that are also biocompatible and easily deployed with catheters in the body. The micron sized interstitial spacing provides a scaffold for ingrowth and migration of cells into the gel matrices.