The profile functions expected in diffraction patterns of axially oriented semicrystalline fibers are discussed. Attention is focused on a Gaussian distribution of the crystallite unique axes. The limits of applicability of known approximations to the computationally demanding theoretical profile function have been found and a simple correction has been proposed enabling the computation of the profile functions near the meridian and on the meridian itself. Test calculations show that this correction leads to better agreement with the theoretical profile functions.