The topotactic thermal decomposition of a synthetic acicular goethite sample into hematite has been studied by controlled rate thermal analysis (CRTA). This method allows a precise, simultaneous and independent control of both the partial pressure of water vapour generated from the decomposition of goethite and the decomposition rate of this precursor. It has been demonstrated that the CRTA method allows obtaining acicular particles of alpha-Fe2O3 with tailored porosity oriented along the c lattice axis (the longest axis of the particle). This finding would be of great potential interest from the point of view of the use of this material as a catalyst.