The radiobiological properties of five newly established carcinoma of the cervix cell lines have been determined. By means of an in vitro clonogenic assay, survival curves were compared at radiation dose rates of 150, 3.2 and 1.6 cGy/min. In terms of both acute radiosensitivity and the extent of low dose-rate sparing, large differences existed among the lines. Two of the lines, HX151c and HX160c, were radiosensitive (surviving fractions at 2 Gy of 0.23 and 0.33 respectively) and showed little radiation recovery capacity during protracted irradiation, whereas the remaining three lines had much higher surviving fraction at 2 Gy (up to 0.6) and showed considerable low dose-rate sparing. The data were well fitted by the Incomplete Repair model of Thames; repair half times ranged from 0.25 to 5.7 h. These findings indicate that large differences in intrinsic radiation recovery capacity exist within this tumour type, differences which emphasise that predictive testing of intrinsic radiosensitivity may be of clinical value in this disease.