Heavy ion irradiation attract a large interest for two applications:radiotherapy and space radiation protection in manned space missions.Exposure to heavy ions radiation results in multiple effects through DNA damage induction.Single-cell gel electrophoresis or comet assay is known for its ability to detect DNA damage at the single cell level and has been used for years to assess DNA damage.It can detect low levels of DNA strand breaks in a short time,just using a few sample cells.DNA double strand breaks(DSBs)are measured at the neutral comet assay condition;under the alkaline comet assay condition both DNA single strand breaks(SSBs)and part DSBs are detected.The two dimensional comet assay is a modification of the two original comet assay,can simultaneously detect DNA SSBs and DSBs in the same human spermatozoa.