Metal or semimetal alkoxides substituted with nonhydrolyzable organic groups are important precursors for inorganic-organic hybrid materials. Understanding the chemistry and structural issues of such precursors is a prerequisite for a rational materials design. Examples are given in this Account, mainly from the chemistry of titanium and zirconium alkoxides, which show that modified metal alkoxide precursors sometimes have an unexpected and unpredictable stuctural chemistry. Furthermore, chemical consequences of the Lewis acidity of the metal alkoxides are discussed, such as adduct formation, ligand exchange reactions, or organic side reactions.