Some additive results on Drazin Inverses ∗ P. Patr´ ıcio a† and R.E. Hartwig b doi: 10.1016/j.amc.2009.05.021 a Departamento de Matem´ atica, Universidade do Minho, 4710-057 Braga, Portugal. e-mail: pedro@math.uminho.pt b Mathematics Department, N.C.S.U., Raleigh, NC 27695-8205, U.S.A. e-mail: hartwig@unity.ncsu.edu Abstract In this paper, some additive results on Drazin inverse of a sum of Drazin invertible elements are derived. Some converse results are also presented. Keywords: Drazin inverse, block matrices AMS classification: 15A09 * Research supported by CMAT - Centro de Matem´ atica da Universidade do Minho, Portugal, by the Portuguese Foundation for Science and Technology – FCT through the research program POCTI, and by Funda¸ c˜ ao Luso Americana para o Desenvolvimento (project # 273/2008). † Corresponding author 1