Brownout occurs when loose sediment on the ground is uplifted by a helicopter during landing or takeoff operations, the consequences of which are severe visual obscurations for the pilots. A Lagrangian dust cloud simulation methodology is described to help better understand the complicated two-phase flow of the rotorcraft brownout problem. The work involved the development of a computationally efficient mesoscale three-dimensional sediment tracking method for low Reynolds number Stokes-type dust flows. For demonstration purposes, the algorithm has been coupled to a free-vortex method that can model in-ground-effect aerodynamics of the rotor system during a series of landing and takeoff maneuvers. The model is matched to models representing the characteristics of the boundary layer on the ground and aspects of the sediment uplift process. Dust cloud simulation techniques developed included representations of particle dynamics using fast numerical methods and the entrainment from saltation and reingestion bombardment. Many of the simulations were computed by using over 200 million particles. Various techniques such as particle clustering methods, the implementation of parallel programming, and optimal use of computer performance using graphic processor units, were developed to limit the computational cost of the simulation while not compromising on the fidelity of the brownout solution. While the resulting simulations of the dust clouds remain tentative, the clouds generated during rotorcraft landing and takeoff maneuvers have been analyzed to better understand the physics behind their development and their sensitivities to the problem parameters. Copyright ©2010 by Syal, Govindarajan & Leishman. All rights reserved.