The fourteen-day kinetics of fluorine (F) elimination in urine was followed up in 24 operators from three main workshops of the plant for phosphorous fertilizers. The concentration of F in urine was determined at the beginning, by 6th h and during the last two hours of a working shift in four successive days and at the beginning of the following production cycle after the discontinuation of the exposure. In parallel, the gas-like fluorine compounds in the air of working environment was also determined. Analogous investigations were performed with a control group--30 non-exposed workers. A potentio-metric method with fluorine-selective electrode was used for the determination of F content in urine and the concentration of the gas-like fluorides in the air. A well manifested tendency to increased excretion was established by the end of the working shift and in the course of the working cycle. The data on the rate of fluorine elimination show that it is the highest during the last two exposure hours, most manifested in the workers from the workshop TSP, less-in the workshop PhA and least--in the workshop NTPP. The concentration of fluorine ions in urine for the three groups of workers investigated, was increased as compared with control values, both by 6th h and during the last two hours.