Abstract: The present invention relates to a sol-gel process for producing monolithic articles of vitreous silica, comprising: preparing a dispersion of silica in water at acid pH; adding to said dispersion at least one alkoxysilane in a quantity such as to obtain a silica:alkoxysilane molar ratio between 6 and 30, and a water:alkoxysilane molar ratio between 40 and 200; modifying the dispersion pH by adding ammonium hydroxide or an amine or an aminoalkyl-alkoxysilane to obtain a sol; pouring the sol thus obtained into a mould; allowing the sol to gel to hence obtain a hydrogel; drying the hydrogel to obtain a dried gel; sintering the dried gel to obtain the vitreous silica article. By implementing this process, even large-dimension vitreous silica monolithic articles can be obtained substantially free of defects, with optimal optical properties, particularly in terms of UV and/or IR radiation transmittance.