Five male volunteers were exposed to benzene vapour (100 mg X m-3) during 2 h singly and during 4 successive days. The mean retention of benzene in the lungs and mean dose amounted to 61% and 74 mg, respectively. Two phases of the excretion of unchanged benzene in the expired air (t 1/2 approximately 2 h and approximately 20 h) and phenol in the urine (t 1/2 approximately 3 h and approximately 12 h) were observed. The observed half time values were similar after single and repeated exposure. Respective values for 4-days experiment amounted to 28 and 47% of the dose absorbed during the last day of exposure. Concentrations of benzene in the expired air and the rate of excretion of phenol in urine were higher after 4-days exposure than after single exposure, which results from benzene toxicokinetics. Coefficients of kinetic processes rate amounted to k2 = 0,15; k3 = 0,07; k4 = 0,06 and sigma kEM = 0,16 X h-1.