Аннотация:This chapter integrates methods of detection of different kinds of DNA damage in cells and tissues. These methods have been used in experimental research, clinical trials and conventional clinical assays over the last few decades. The most commonly used techniques were developed on the base of DNA damage–induced modification of histone H2AX and DNA repair proteins involved in different mechanisms of DNA lesion elimination. Special attention is paid to immunological methods of monitoring DNA damage and repair in single cells. These methods are considered to be the most sensitive for detection of low levels of DNA damage and could be used for estimation of radiation health risk, for cancer diagnostics and determination of effectivity of cellular response to chemotherapy.