BACKGROUND: Adaptation to exercise stands for body's physiological response to training. The process through which the body becomes acclimated to a specific exercise or training regimen through repeated exposure is referred to as the principle of adaptation. This study aims to assess the effect of exercise on haemoglobin concentration and some other haematological parameters in trained and untrained male individuals. METHODS: Healthy trained and healthy untrained men were selected, who fulfilled the inclusion criteria and after that blood sample were taken by the cooperation of Biochemistry and Pathology department. From the blood sample Hb, MCV, MCHC, and MCH were calculated.