This paper describes a general procedure for the formation of hydrogels that contain microfluidic networks. In this procedure, micromolded meshes of gelatin served as sacrificial materials. Encapsulation of gelatin meshes in a hydrogel and subsequent melting and flushing of the gelatin left behind interconnected channels in the hydrogel. The channels were as narrow as approximately 6 microm, and faithfully replicated the features in the original gelatin mesh. Fifty micrometre wide microfluidic networks in collagen and fibrin readily enabled delivery of macromolecules and particles into the channels and transport of macromolecules from channels into the bulk of the gels. Microfluidic gels were also suitable as scaffolds for cell culture, and could be seeded by human microvascular endothelial cells to form rudimentary endothelial networks for potential use in tissue engineering.