Purpose: To establish 60Co γ-ray dose-response curves for dicentrics and translocations visualized by chromosome painting and for dicentrics analysed after conventional solid staining. Materials and methods: Analysis of chromosomal aberrations was performed on peripheral blood lymphocytes obtained from 48 h old cultures of irradiated whole blood. Dicentrics were scored from Giemsa-stained preparations, and bi-coloured dicentrics and translocations after FISH painting of chromosomes 1, 2 and 4. Results: Equal frequencies of complete dicentrics and translocations, where both members of the exchanges were seen, were observed in the chromosome painting analysis at all doses, resulting in similar calibration curves. Due to differences in scoring criteria, dicentrics scored in conventionally Giemsa-stained slides agreed better with data for total than for complete exchanges. Donor differences for translocations at the control level and at low doses were seen and large uncertainty surrounds the linear component of the dose- response for total translocations. Conclusions: Dose reconstruction of past exposures in cases of low doses is very dependent on the linear coefficient of the curve. Results: indicate that total translocations would give less reliable dose estimates and therefore complete translocations are preferred.