Abstract: Pollutant dispersion models in the atmosphere can be described by Eulerian or Lagrangian approaches. Eulerian models are precise and could have a lower computation demanding; Lagrangian models can be more expensive from computational point of view, but they provide good simulations over complex terrain. A parallel version of the Lagrangian particle model – LAMBDA – is developed using the MPI message passing communication library. Performance tests were executed in a distributed memory parallel machine, a multicomputer based on IA-32 architecture. Portions of the pollutant in the air are considered particles emitted from a pollutant source, evolving under stochastic forcing. This yields independent evolution equations for each particle of the model, that can be executed by a different processor in a parallel implementation. Speed-up results show that the parallel implementation is suitable for the used architecture.