The most difficult technical challenge for surface irradiation of fruits and vegetables is the need to achieve a uniform dose over the entire surface of convoluted shapes. The main goal of this research was to calculate the dose distribution produced by low energy electron irradiation of a typical complex shape, an apple, using Monte Carlo simulation. In this study, Monte Carlo simulation was used to determine the dose distribution at the surface of an apple irradiated with e-beam generated by a Van de Graaf accelerator (1-2 MeV). The dose distribution was used to develop the best irradiation angle while rotating an irregularly shaped food material (the apple) for uniform surface irradiation. A software package, Monte Carlo N-particle, was used to simulate an electron beam irradiation with a 1.0, 1.5 and 2.0 MeV sources on an apple. The apple structure was simulated by creating 3-D apple-like shape geometry by joining two spheres of 3.2 cm of radius each. The entire body is centered at the origin and the spheres are centered at -1.2 and 1.2 cm on the y-axis in the z-y-plane. As the apple is tilted towards the source, the dose gets distributed mainly in the front top region of the apple. Likewise, as the apple is tilted against the source, the dose gets distributed primarily in the lower front portion of the apple. A combination irradiation treatment with the axis of the apple tilted 30degrees against and 30degrees towards the source irradiation position after one full revolution resulted in the most uniform dose distribution for the three energies source tested. The average dose at the surface of the front of the apple was in the range from 1.2 to 1.6 kGy and 3.6 to 4.0 kGy at the surface of the top and bottom. (C) 2003 Elsevier Science Ltd. All rights reserved.