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A numerical model is used to investigate the dependence at 351 nm of desert-aerosol extinction and backscatter coefficients on particle imaginary refractive index (m(i)). Three ranges (-0.005 less than or equal to m(i) less than or equal to -0.001, -0.01 less than or equal to m(i) less than or equal to -0.001, and -0.02 less than or equal to m(i) less than or equal to -0.001) are considered, showing that backscatter coefficients are reduced as Imi increases, whereas extinction coefficients are weakly dependent on mi. Numerical results are compared with extinction and backscatter coefficients retrieved by elastic Raman lidar measurements performed during Saharan dust storms over the Mediterranean Sea. The comparison indicates that a range of -0.01 to -0.001 can be representative of Saharan dust aerosols and that the nonsphericity of mineral particles must be considered. (C) 2004 Optical Society of America.