Abstract: Anything that poses a challenge or a threat to the well-being is a stress. Understanding the genetic material and cellular response of rats threatened with repeated swim stress provides insights that can influence human healthy. The aim of the present study was to assess the genetical damage and cytological changes caused by exposure of the test organism (Rattus rattus) to forced swim stress. For this purpose, animals have been submerged in water path 15 min daily for 2 weeks. Following that we performed a Micronuclei (MN) test using MNNCE (Micronucleated Normocromatic Erythrocytes) and MNPCE (Micronucleated Polychromatic Erythrocytes), NDI (Nuclear Division Index) and cytological parameters using NDCI (Nuclear Division Cytotoxicity Index), necrotic and apoptotic cells in rat’s bone marrow samples. Results showed that there was a slightly but not significant increase in the frequency of micronucleated as well as in cytological parameters in bone marrow cells. In light of these results if the time-influence taken account forced swim stress may be considered unsafe suffering for a long time.