The aim of this paper is to present the results of characterization of the particle shapes of six standard transition aluminas samples using transmission and scanning electron microscopies; selected area electron diffraction, in parallel with X-ray powder diffraction were used for confirmation of the different transition aluminas types. The transition aluminas - chi; kappa; gamma; theta; delta; and eta were supplied by ALCOA Central Laboratory. The chi-; kappa-;gamma- and delta-Al(2)0(3) microcrystals are pseudomorphs from their respective precursors gibbsite and boehmite. However, theta-Al(2)0(3) microcrystals are not pseudomorphs after the standard delta-Al(2)0(3) sample. Also, eta-Al(2)0(3) are not pseudomorphs after bayerite somatoids.