The Mullins-Sekerka problem for closed interfaces is widely studied since it appears naturally as a gradient flow of the area functional, as a sharp interface limit of the Cahn-Hilliard equation, and in physical models of phase changes. In this talk I will address the Mullins-Sekerka problem for interfaces with a ninety degree contact angle. In particular, I will show existence and uniqueness of strong solutions and discuss stability properties. If time permits, I might also talk a bit about recent progess in Mullins Sekerka/Navier-Stokes problems with contact angle. This is joint work with Helmut Abels, Harald Garcke, and Mathias Wilke.