The wavelengths of the TOMS channels can be optimized to minimize the effects of random measurement errors on simultaneous ozone and sulfur dioxide retrievals. The inversion matrix is extremely sensitive to the spectral position of the channels due to mathematical singularities related to O3 and SO2 absorption coefficients. None of the current sets of wavelengths in the TOMS instruments are optimal for the low latitude retrievals considered. Minor adjustment of the wavelengths can reduce retrieval errors by more than a factor of two.¿ 1997 American Geophysical Union