Abstract. Green's formulas for elliptic cone differential operators are established. This is achieved by an accurate description of the maximal domain of an elliptic cone differential operator and its formal adjoint; thereby utilizing the concept of a discrete asymptotic type. From this description, the singular coefficients replacing the boundary traces in classical Green's formulas are deduced.1. Introduction 1.1. The main result. Let X be a compact C ∞ -manifold with non-empty boundary, ∂X. On the interior X• := X \ ∂X, we consider differential operators A which on U \ ∂X for some collar neighborhood U ∼ = [0, 1) × Y of ∂X, with coordinates (t, y) and Y being diffeomorphic to ∂X, take the formSuch differential operators A are called cone-degenerate, or of Fuchs type, and this is written as A ∈ Diff µ cone (X). They arise, e.g., when polar coordinates are introduced near a conical point.Throughout, we shall fix some reference weight δ ∈ R. This means that we will be working in the weighted L 2 -space H 0,δ (X) as the basic function space; see (1.12) and also Appendix B. Let A * ∈ Diff µ cone (X) be the formal adjoint to A, i.e,where ( , ) denotes the scalar product in H 0,δ (X). Then it is customary to consider the maximal and minimal domains of A,