Multiple-endpoint follow-up genotoxicology monitoring was performed in a group of 22 Hungarian road pavers between 1996 and 1999. The studied endpoints were the determination of structural and numeric chromosome aberration (CA), sister chromatid exchange (SCE), high-frequency SCE and HPRT mutation frequencies, and ultraviolet (UV)-light-induced unscheduled DNA synthesis in peripheral blood lymphocytes (PBLs). The workers (8 hand pavers and 14 finishers, mean age 37 yr) used tar-free asphalt. The results were compared with those of 6 work-site controls (35 yr), 101 historical controls (38 yr), and 87 industrial controls (38 yr). The most marked changes were found in the CA frequencies. In the control, the mean CA frequency was 1.6%. In the first study, increased CA frequencies were found in the donors that either had been exposed to hot asphalt fumes or had cleaned the equipment with crude oil. The mean CA frequency of the 14 finishers working in closed cabins was 3.67% in 1996. The increased CA frequency was attributed to the high level of hot asphalt fumes due to insufficient ventilation. By 1999 the mean CA frequency decreased to 1.23%. For the 8 hand pavers working in open air the mean CA frequency was 3.6% in 1996. The obtained data suggested that the increase in CA frequencies was due to the use of petroleum and crude oil; therefore, these substances were replaced with harmless detergents. By 1999 the mean CA frequency decreased to 1%. In finishers the mean CA frequency returned to the control level 1 yr later (1999) than in the case of hand pavers. The chromosome-type aberrations remained predominant during the follow-up. The individual variations observed were attributed to smoking and inadequate personal protection. The obtained results suggest that the use of tar-free asphalt and harmless detergents with adequate personal protection does not increase the frequencies of the genotoxicological parameters compared to controls. Consequently, an improvement in working conditions can prevent further exposures and thus decrease the cancer risk of road pavers.