Abstract: Slowly polymerizing hydrogels are provided which are useful as a means of delivering large numbers of isolated cells via injection. The gels promote engraftment and provide three dimensional templates for new cell growth. The resulting tissue is similar in composition and histology to naturally occurring tissue. This method can be used for a variety of reconstructive procedures, including custom molding of cell implants to reconstruct three dimensional tissue defects, as well as implantation of tissues generally. The polymers permit construction of muscle and cartilage tissues which are useful to repair defects such as reflux and incontinence.