The development of the Molecular Gas-Phase Documentation database is briefly described. It has been developed from a unique literature compilation via the first client programs on computer mainframes and personal computers to a versatile HTML-based version, which can be run platform-independently by common Web browsers. In the database, the structural parameters for about 9200 organic, metalorganic, and inorganic compounds studied in the gas phase mainly by electron diffraction and microwave spectroscopy are given numerically, and the molecular structures can be visualized in many ways, particularly in three-dimensional representation. Moreover, the spectroscopic parameters (such as rotational and centrifugal distortion constants, dipole moments, nuclear quadrupole coupling constants, and barriers of hindered rotation) can be retrieved by keywords.