In a group G, u(m)(G) denotes the subgroup of the elements which normalize
every subnormal subgroup of G with defect at most m. The m-Wielandt series
of G is then defined in a natural way. G is said to have finite m-Wielandt
length if it coincides with a term of its m-Wielandt series. We investigate
the structure of infinite groups with finite m-Wielandt length.