A large variation in the dispersion data for AlxGa1.0-xN epitaxial layers is presented. An experimental study is conducted which no(λ) and ne(λ) were measured to an accuracy of approximately ±0.01 for five AlxGa1.0-xN MOCVD-grown layers on sapphire substrates with 450<λ<980 nm. The uncertainty in the index of the rutile TiO2 prism limited the absolute accuracy of the measurements. The relative accuracy between the dispersion curves is approximately ±0.0005 and the accuracy of the Al molar concentration x is ±10%. Simple functions were discussed that allow convenient calculation of the refractive indices as functions of x and λ.