On the lower Nil-groups of Waldhausen

Let Gamma = Gamma (0) *(G) Gamma (1) be an amalgamated free product, where G is a finitely generated central subgroup of Gamma (0) and Gamma (1). We s how that the negative Waldhausen Nil-groups that appear in the calculation of the K-theory of Z Gamma vanish. If G = H x T-m is a decomposition of G w ith H a finite group and T the infinite cyclic group, we also show that the exponent of the NK0-group depends on the order of H.