  We use logarithmic {\ell}-class groups to take a new view on Greenberg's
conjecture about Iwasawa {\ell}-invariants of a totally real number field K. By
the way we recall and complete some classical results. Under Leopoldt's
conjecture, we prove that Greenberg's conjecture holds if and only if the
logarithmic classes of K principalize in the cyclotomic Z{\ell}-extensions of
K. As an illustration of our approach, in the special case where the prime
{\ell} splits completely in K, we prove that the sufficient condition
introduced by Gras just asserts the triviality of the logarithmic class group
of K.Last, in the abelian case, we provide an explicit description of the
circular class groups in connexion with the so-called weak conjecture.
