Cellulose nitrate films (commercially available as LR 115 films were irradiated systematically with alpha particles in the energy range from 1 to 5 MeV with incident angles from 30 degrees to 90 degrees. After etchin to remove a thickness of 6.5 mu m, the lengths of the major and minor axes of the alpha-particle track openings in the films were measured with an image analyser under an optical magnification of 10(3). These data were used altogether to derive a V function (ratio between the track etch rate and the bulk etch rate), which took the functional form of the Durrani-Green's function, i.e., V = 1 + (a(1) exp(-a2R') + (a(3) exp(-a(4)R'))(1 - exp(-a(5)R')), but with new constants as a(1) = 2.14, a(2) = 0.12, a(3) = 2.7 and a(4) = 0.135 (a(5) = 1). We then went on to correct for the different etched thickness for different datasets. With these corrections, the experimental data were found to fit the model very satisfactorily. It was also interesting to see that the range of the calculated etched layer was consistent with the expected range. (c) 2005 Published by Elsevier B.V.