[en] Purpose: To study the relationship between residual DNA damage and clonogenic measurements of radiosensitivity in fibroblasts from pretreatment cervix cancer patients. Methods and Materials: Early passage vaginal fibroblasts from nine preradiotherapy cervix cancer patients and two radiosensitive skin fibroblast cell strains were studied. Cell survival was measured by clonogenic assay following both high and low dose rate irradiation. Residual DNA damage was measured using pulsed-field gel electrophoresis (PFGE) after irradiating radiolabeled, plateau-phase cells at 37 deg. C and allowing 24 h for repair. DNA damage was expressed both in terms of the residual damage slope (fitted to data from 60 to 150 Gy) and the fraction of activity released (FAR) following 150 Gy. Results: The surviving fraction at 2 Gy (SF₂) values after high dose rate irradiation for the vaginal fibroblasts ranged from 0.15 to 0.32 (a 2.2-fold difference). When the two radiosensitive cell strains were included, residual damage, expressed as the residual damage slope, correlated with α (r = 0.82, p = 0.002), D bar (r = -0.91, p < 0.001) and SF₂ (p = -0.79, p = 0.004), and when the vaginal fibroblasts alone were studied, the residual damage slope again correlated with clonogenic survival, although less strongly [α (r 0.66, p = 0.053), D bar (r = -0.83, p = 0.006), and SF₂ (r = -0.63, p 0.07)]. Within the group of vaginal fibroblasts there was a 4.0-fold difference in residual DNA damage slope. When residual damage was expressed as FAR at 150Gy, then for all cell strains the correlations were α: r 0.78, p 0.004, D bar: r = -0.86, p = 0.001, and SF₂: r = -0.78, p = 0.004, and for the vaginal fibroblast strains alone the correlations were α: r = 0.60, p = 0.088, D bar: r = -0.75, p = 0.02, and SF₂: r = 0.62, p = 0.077. Conclusion: This study confirms previous findings that residual DNA damage correlates with clonogenic survival in fibroblasts. In addition, it demonstrates a correlation for fibroblasts from pretreatment cervix cancer patients demonstrating a relatively small range of SF₂ values