Abstract: The paper introduces our achievements in the application of radioisotopic tracer techniques to: (1) the study on the migration of calcium in soil with ~(45)Ca, (2) studies of adsoption, migration and persistence of toluene and ethylene dichloride in soil using ~(14)C labelled compound, (3) study on the biodegradation pathway of Terephthalic Acid in anaerobic reactor using double-labelling method, (4) the uptake, transmission and release of ~(18)F in Tilapin fish, (5) the determination of the filtration velocity, flow direction and dispersion coefficient in the groundwater with ~(131)I, in order to predict the pollution of groundwater, and (6) the measurement of flow distribution in an upflow anaerobic sludge blanket reactor using ~(131)I.