A method for rapidly casting patterned vascular networks in engineered 3D tissues is described. The approach involves 3D printing a rigid carbohydrate glass lattice, which serves as a sacrificial template for creating perfusable vascular channels. The lattice is dissolved in the presence of living cells, leaving behind a network of channels that can be lined with endothelial cells and perfused with blood under high-pressure pulsatile flow. This method allows for independent control of network geometry, endothelialization, and extravascular tissue, making it compatible with a wide variety of cell types, synthetic and natural extracellular matrices (ECMs), and crosslinking strategies. The carbohydrate glass is formed by dissolving carbohydrates in water and boiling the solvent, and its properties were optimized by adding starch, glycerol, and dextran to achieve the desired mechanical stiffness and biocompatibility. The lattice is then used as a sacrificial element to create vascular channels within monolithic cellularized tissue constructs. The process involves encapsulating the lattice in ECM along with living cells, crosslinking the ECM, and dissolving the lattice to form the vascular channels. The resulting tissue constructs support convective and diffusive transport of nutrients and metabolic byproducts, and maintain the metabolic function of primary rat hepatocytes in engineered tissue constructs. The method is compatible with a wide range of ECM materials, including those crosslinked by photopolymerization, ionic interactions, enzymatic activity, and protein precipitation. The approach allows for the creation of complex cellular and immobilized factor gradients in tissue constructs, and demonstrates the ability to support the function of engineered tissues comprised of even highly sensitive primary cells. The method is also rapid and efficient, allowing for the fabrication of perfusable vascular networks in minutes, and is compatible with a wide range of cell types and ECM materials. The results demonstrate the potential of this approach for the development of functional 3D cell cultures at or near physiologic cell densities.A method for rapidly casting patterned vascular networks in engineered 3D tissues is described. The approach involves 3D printing a rigid carbohydrate glass lattice, which serves as a sacrificial template for creating perfusable vascular channels. The lattice is dissolved in the presence of living cells, leaving behind a network of channels that can be lined with endothelial cells and perfused with blood under high-pressure pulsatile flow. This method allows for independent control of network geometry, endothelialization, and extravascular tissue, making it compatible with a wide variety of cell types, synthetic and natural extracellular matrices (ECMs), and crosslinking strategies. The carbohydrate glass is formed by dissolving carbohydrates in water and boiling the solvent, and its properties were optimized by adding starch, glycerol, and dextran to achieve the desired mechanical stiffness and biocompatibility. The lattice is then used as a sacrificial element to create vascular channels within monolithic cellularized tissue constructs. The process involves encapsulating the lattice in ECM along with living cells, crosslinking the ECM, and dissolving the lattice to form the vascular channels. The resulting tissue constructs support convective and diffusive transport of nutrients and metabolic byproducts, and maintain the metabolic function of primary rat hepatocytes in engineered tissue constructs. The method is compatible with a wide range of ECM materials, including those crosslinked by photopolymerization, ionic interactions, enzymatic activity, and protein precipitation. The approach allows for the creation of complex cellular and immobilized factor gradients in tissue constructs, and demonstrates the ability to support the function of engineered tissues comprised of even highly sensitive primary cells. The method is also rapid and efficient, allowing for the fabrication of perfusable vascular networks in minutes, and is compatible with a wide range of cell types and ECM materials. The results demonstrate the potential of this approach for the development of functional 3D cell cultures at or near physiologic cell densities.