A new approach to the classic closure problem for turbulent boundary layers is presented. This involves using the well known mean-flow scaling laws such as Prandtl's law of the wall and the law of the wake of Coles together with the mean continuity and the mean momentum differential and integral equations. The important parameters governing the flow in the general non-equilibrium case are identified and are used for establishing a framework for closure. Initially closure is done here empirically from limited data but the frame work is most suitable for applying the attached eddy hypothesis in future work. How this might be done is indicated . All of this is applied to both adverse and favorable pressure distributions.