Chemotherapy and radiotherapy are widely accepted as common forms of treatment for cancers. The majority of cancer patients receive chemotherapy alone or in combination with radiotherapy. Most chemotherapeutic drugs cause DNA damage to the rapidly dividing cancer cells but normal cells are also damaged in the process. Therefore DNA repair levels in tumour and normal cells may determine the success of the treatment. The aim of this work was to evaluate the use of DNA repair biomarkers for assessing responses to chemotherapeutic drugs. The novel technique of imaging flow cytometry was employed to analyse the induction and resolution of γ-H2AX and RAD51 DNA repair biomarkers in DNA repair normal cell lines MRC5-SV1 and NB1-HTERT, an ATM-deficient cell line AT5BIVA (derived from an Ataxia Telangiectasia patient) and an XPF-deficient cell line GM08437B. Two cell lines were also developed, MRC5-SV1R and NB1-HTERTR which had been made resistant to HN2. A range of chemotherapeutic drugs, Adriamycin, Cisplatin and Nitrogen Mustard which have different modes of action were examined in this work. We have demonstrated distinct differences in γ-H2AX and RAD51 foci induction and resolution between the two DNA repair normal cell lines following exposure to different chemotherapeutic drugs. Additionally, it was demonstrated that both the resistant and sensitive cell lines have elevated γ-H2AX and RAD51 expression profiles in comparison to the parental cell lines over a 48 hour period post treatment with the cross-linking agent HN2. It is concluded that while both the γ-H2AX and Rad51 biomarkers may be useful for determining chemotherapeutic response, a larger cohort of cell lines and tumour samples is required for further analysis.