We provide a general overview of the evolution of vortex string networks and of their cosmological consequences. We describe the velocity‐dependent one‐scale model for string evolution and use it to discuss their basic large‐scale features. We discuss their basic cosmological consequences, in particular for the cosmic microwave background. We also briefly review other cosmological implications such as primordial backgrounds of gravitational waves and ultra‐high energy cosmic rays. © 2004 American Institute of Physics