This article reexamines systematically the theory of nearby cycles of
holonomic D-modules. The theory is extended to complexes, and one gets
an equivalence of categories between monodromic complexes and special
izable complexes (the last ones, taken on the completion of D for the
V-filtration). In particular, one gets the theorems of commutation wit
h duality, smooth inverse images, and proper direct images which were
natural to expect.