The 2400 MWth Gas-Cooled Fast Reactor (GCFR), with plate-type carbide/SiC CERCER fuel, is an innovative design exhibiting many attractive features among which sustainability achieved with an internal breeding gain close to zero and feedback coefficients enabling an excellent behavior under some safety transients. This paper summarizes the analytical results of an international benchmark exercise being set up within the European Union to verify the neutronic tools and associated nuclear data libraries currently used for helping in finalizing the design of the GCFR within the European Union. A rather simple homogenized 2D model has been specified for the first phase of this benchmark. The computational tools being used in the analysis include both a stochastic and a deterministic code, MCNP and ERANOS, respectively, with nuclear data essentially based on the JEF-2.2 data library. The overall results indicate that the agreement of the solutions provided by the different participants is satisfactory. The most significant discrepancy, which can be partly attributed to different ERANOS options, is observed in the case of the end of life reactivity and amounts to a few dollars. The rather positive outcome of this initial phase of the benchmark has allowed identifying deficiencies in the analytical tools and serves as a basis for the definition of subsequent phases. It might also help to identify potential ways to improve the design.