Mobilities of some organic and inorganic ions produced on interaction with -radiations from tritium in air (saturated with water vapor) have been measured. The negative ions generated were allowed to move in the electrical field and collected at the oppositely charged electrode. The mobility of negatively charged ions of air is found to be 2.18 (cm·s–1/V·cm–1), which is in fair agreement with the reported value of 2.2. The calculated mobilities of other ions based on the measured drift time exhibit a variation of up to 6.8 cm s–1·V cm–1. The occurrence of electrophilic sites or repeated presence of more electronegative atoms and or groups in the molecular structure gave higher mobilities. The consideration of parachors, electron affinities and dipole moments of the respective compounds do not reveal any trend.