The four-dimensional Green-Schwarz anomaly cancellation mechanism with a surviving U(1) gauge group is described in the context of standard tensor calculus (superspace) techniques for local supersymmetry. This phenomenon is "dual" to the case in which a massless vector field is eaten up by an antisymmetric tensor which thereby describes a massive spin-one field. Both mechanisms are motivated by recent string-loop calculations. Unlike the case of some supergravity models, these mechanisms seem unable (order by order, at least) to break supersymmetry while keeping the cosmological constant vanishing.
