A major step towards the understanding of differential operators on singular manifolds consists in the construction of algebras of pseudodifferential operators that will allow the solution of natural elliptic equations in terms of parametrix constructions. This leads to questions of elliptic regularity, Fredholm and index theory. The volume contains contributions to the theory of boundary value problems without the transmission property under the aspect of variable branching asymptotics, on commutator characterizations in and the submultiplicativity of Boutet de Monvel's algebra, the construction of a pseudodifferential calculus for boundary value problems on manifolds with conical singularities, and on heat kernel estimates for elliptic singular operators. Contributions from the area of Mathematical Physics address the problems of reduction and eigenstates in deformation quantization and spectral theory for SchrAdinger operators with electromagnetic potential.