The critical pressures and the critical temperatures of ten tetraalkoxysilanes (tetraalkyl esters of silicic acid) Si[O(CH2)(n)H](4) with n = 1 to 10 have been measured. All the substances studied begin to decompose at temperatures below their critical points. The method of pulse-heating applicable to thermally unstable compounds has been used. Residence times were from (0.03 to 1) ms, which resulted in little decomposition of the substances during measuring. The experimental critical properties of tetraalkoxysilanes have been compared with the values estimated by the group-contribution methods of Lydersen and Nannoolal et al.