Broadband antireflection schemes for silicon surfaces based on the moth-eye principle and comprising arrays of subwavelength-scale pillars are applicable to solar cells, photodetectors, and stealth technologies and can exhibit very low reflectances. We show that rigorous coupled wave analysis can be used to accurately model the intricate reflectance behavior of these surfaces and so can be used to explore the effects of variations in pillar height, period, and shape. Low reflectance regions are identified, the extent of which are determined by the shape of the pillars. The wavelengths over which these low reflectance regions operate can be shifted by altering the period of the array. Thus the subtle features of the reflectance spectrum of a moth-eye array can be tailored for optimum performance for the input spectrum of a specific application.