Alterations in blood rheology under the influence of anesthesia have been observed and discussed among the responsible factors for the deterioration of tissue and organ perfusion related to anesthetic procedures. Sevoflurane is one of the volatil anesthetics which is being used very common in surgery. In this study, the effects of sevoflurane anesthesia were investigated in different age groups of rats. 22 male rats were used in the study and the rats were divided into two groups according to their age (young and old) comprising of two subgroups in each. First group was the young control (n=5), the second was the young group treated with sevoflurane (n=5), the third group was the old control (n=7) and the last group was the old group treated with sevoflurane (n=5). %2 of sevoflurane was applied to the rats with inhalation in a adjustable cage for one hour. The deformability indexes of the erythrocytes were measured by a laser diffractometer (Myrenne Rheodyne SSD). Deformability indexes of red blood cells were significantly decreased with sevoflurane in old rats (p=0.028) whereas it had not any significant effect in young group compared with their controls. When we compared the young and old control groups, the deformability indexes were significantly higher in old ones (p < 0.001). However, there were not any significant difference between the old and the young sevoflurane applied groups. A volatil anesthetic agent sevoflurane has impaired the deformability of erythrocytes in old rats compared to their controls, whereas it had not any significant effect in young ones which may be due to the flexibility of the young erythrocytes leading them to tolerate to the environmental changes. These results reveal that the inhalation anesthetics like sevoflurane may cause more serious problems in the elder people and their hemodynamic parameters should be checked more seriously during the surgery.