Self-organization theory provides a framework for transferring non-linear dynamic models from physical sciences towards social sciences, especially urban geography. The compatibility of this theory with observed features of change in spatial systems is analysed. A provisional evaluation of the main applications to the structuring of cities and systems of cities is tempted. The heuristic and pedagogical advantages of those models are underlined. They can produce qualitative change stemming from small quantitative variations in some parameter values. However, there are limitations to the analogy between physical and geographical systems. Experimental results lead to revise those models in the light of an evolutionary theory. They should include the creative and cognitive behaviours which characterize the genesis of complexity in spatial systems.