We propose a general method to construct new triangulated categories, relative stable categories, as additive quotients of a given one. This construction enhances results of Beligiannis, particularly in the tensor-triangular setting. We prove a birationality result showing that the original category and its relative stable quotient are equivalent on some open piece of their spectrum. Contents 1. Introduction 1 2. Preliminaries 4 3. Proper classes of triangles 5 4. Beligiannis' construction 9 5. Thick subcategories and proto-birationality 15 6. Algebraicity 19 7. Tensor-triangulated stable categories 21 8. Thick tensor-ideals and birationality 25 References 29