BOT3P Version 1.0 was originally conceived as a set of standard FORTRAN 77 language prograrms in order to give the users of the DORT and TORT deterministic transport codes some useful diagnostic tools to prepare and check their input data files. Later versions extended the possibility to produce the geometrical, material distribution and fixed neutron source data to other deterministic transport codes such as TWODANT/THREEDANT of the DANTSYS system, PARTISN and, potentially, to any transport code through BOT3P binary output files that can be easily interfaced (see, for example, the case of the Russian two-dimensional (2D) and three-dimensional (3D) discrete ordinates neutron, photon and charged particle transport codes KASKAD-S-2.5 and KATRIN-2.0). Later BOT3P versions further improved the geometrical capabilities with the possibility to realise in a new model geometries caming from other DORT/TORT input files, to include data derived from computerized tomography (C.T.) scans, to model a reactor care by preserving exactly the single rod volume and to generate the geometrical entries for the sensitivity code SUSD3D and a geometrical input far the MCNP Monte Carlo transport (in case of X-Y-Z mesh grid). BOT3P Version 5.0 contains important additions, such as new 2D and 3D graphics options and the possibility to directly manage and plot 2D R-Z geometries. Users can optionally require as refined a computation as desired of the area/volume error of material zones with respect to the theoretical values (approximation due to the stair-cased geometry representation) and the automatic correction of material densities in order to globally conserve masses. A binary file is optionally written with the density distribution of the different materials contained in the single mesh, allowing also a local density correction (per mesh). BOT3P was developed on a DIGITAL UNIX ALPHA 500/333 Workstation and successfully used not only in some complex neutron shielding and criticality benchmarks but also in power reactor applications. BOT3P was also tested on Red Hat Linux 7.1 and is designed to run on most UNIX platforms. All BOT3P versions are publicly and freely available from OECD/NEA Data Bank.