[en] The variations of radon concentration in well waters have been used as a precursor of an oncoming earthquake. A closed circuit technique of radon measurement is used to monitor radon in water from a bore well at Pyntheromukrah, Shillong. The variation of 35 to 210 alpha counts per 50 seconds of the radon concentration in the water has been correlated to the local earthquake monitored by the Indian meteorological Department at Upper Shillong and to the meteorological variations which might have affected it. Though no major event has taken place during the period of two years of observation, a fair degree of correlation is observed with earthquakes of medium magnitude taking place even at large distances. The importance of this paper is restricted to a large extent on the development of the technology of radon monitoring for earthquake prediction. 7 refs., 4 figures, 1 table. (author)