We report the results from an investigation of the effects of variations in layer thicknesses during the growth of semiconductor Bragg mirrors on their reflectivity spectra. Different types of variations are investigated and an effort is made to point out the sources of such errors in a typical growth process. It is expected that this study will shed light on the critical control parameters for very highly reflecting mirrors and help the interpretation of the measured spectra from a finished growth run and the identification of the possible sources of deviations from the ideal structure. ©1995 American Institute of Physics.