Niobium is known to be a very powerful alloying element by which various processes such as recrystallisation, grain growth, transformation, precipitation can be affected and controlled in an effective manner. This leads to a significant effect on the evolution of the microstructure and on the mechanical properties. Steels that contain additions of niobium display elevated yield and tensile strength values and only a slight decrease in ductility. In this paper the effect of niobium on the TRIP effect and the mechanical behaviour of multi phase high strength steels was examined. Annealing simulations were performed, the microstructure development was analysed. It can be concluded that niobium exerts a remarkable influence on the various transformations in general and the carbon enrichment of the austenite and on martensite nucleation in particular. The addition of niobium renders process control often much easier, allows less demanding process routes and can lead to a further improvement of the favourable mechanical properties of TRIP aided multi phase steels.