The correlation between grain size, optical birefringence, and transparency is discussed for tetragonal zirconia (ZrO(2)) ceramics using the Mie, Rayleigh, and Rayleigh-Gans-Debye scattering models. Our results demonstrate that at the degree of mean birefringence in the range (0.03-0.04) expected for tetragonal ZrO(2), only the Mie theory provides reasonable results. At small particle size (< 50 nm) the more straightforward Rayleigh approximation correlates with the Mie model. A real in-line transmission of similar to 50% at visible light and 1 mm thickness is expected at a mean grain size < 40 nm and similar to 70% at a mean grain size < 20 nm. At an infrared (IR) wavelength of 5 mu m there should not be any scattering caused by birefringence for grain sizes < 200 nm. Our simulations were validated with experimental data for tetragonal ZrO(2) (3 mol% Y(2)O(3)) ceramics made from a powder with an initial particle size of similar to 10 nm by sintering in air and using hot-isostatic pressing. The maximum in-line transmission of about 77% was observed at IR wavelengths of 3-5 mu m.