Ionizing radiation is a strong physical mutagen, causing breakage of phosphodiester bonds in DNA at any stage of the mitotic cycle. Analysis of sister chromatid exchange (SCE) has come into use as a sensitive DNA-damage indicator. We investigated the SCE rates in radiology technologists who are occupationally and chronically exposed to ionizing radiation. The study included 39 radiology technologists and 35 sex- and age-matched healthy controls. There was a statistically significant difference in the SCE frequency between radiology technologists and controls (p < 0.0001). Additionally, previous SCE data of 10 radiology technologists were compared with current results regarding radiation exposure time. There was statistically significant difference between previous and current SCE values (p = 0.005). The significant increase in the frequency of SCE in radiology technologists emphasizes the importance of radiation–protection procedures in order to minimize radiation exposure and avoid possible genotoxic effects. Comparison of two studies that measured SCE values of radiology technologists after 8 years also suggests that the genotoxic effect is reversible. In conclusion, radiation is still an important mutagenic agent despite improvements in daily working hours and conditions.