The review surveys the pathways of formation of crystalline oligomeric oxoalkoxides MmOn(OR)p, which are products of partially controlled (or uncontrolled) hydrolysis, oxidation, thermal decomposition of mono- and bimetallic alkoxides of the ortho series M(OR)n and MmM'n(OR)p or elimination of ethers from these compounds. The physicochemical properties of oxoalkoxides (solubility, the behaviour in solutions, volatility, etc.) differ considerably from the properties of the corresponding alkoxides. Hence, oxoalkoxides can be considered as immediate precursors of oxide materials produced by sol-gel technology. The MmOn(OR)p compounds are classified according to the sizes of associates. The crystal chemistry of alkoxides is discussed.