Background: Petrol is known to be hazardous to human health and is associated with various health effects, such as haematotoxicity and oxidative stress. Although Malaysia has adopted the European fuel quality standards in recent years in order to reduce petroleum pollutants and to improve air quality, gasoline with research octane number 95 (RON95), believed to contain benzene and other toxic substances, is still widely used all over the country. This study assessed the effect of RON95 gasoline on haemtological parameters of rats after 11 weeks of exposure. Methods: A total of 16 male Sprague-Dawley rats were randomly divided into two groups: control (exposed to ambient air daily) and gasoline exposed (exposed to petrol fumes at 11.13 ± 1.1cm3/h for 6h daily, 6 days/week) groups. Body weight was monitored daily. At the end of 11 weeks, the rats were sacrificed, bone marrow was extracted for cytological examination, and blood samples were collected for a full blood picture examination, full blood counts and oxidative markers. Results: The results show that gasoline inhalation was associated with a significant (P < 0.05) reduction in the rate of weight gain and a reduction in mean corpuscular haemoglobin concentration and red cell distribution width. It was also observed that the inhalation of gasoline was associated with changes in the nuclei of megakaryocytes, hence causing an increase in the percentage of abnormal megakaryocytes with detached nuclei, hypo-lobulation and/or disintegration. However, the inhalation of gasoline did not cause significant changes in oxidative markers in the erythrocytes. Conclusion: This study shows that 11 weeks of inhaling RON95 petrol vapours caused adverse effects on weight gain, blood cell indices and bone marrow megakaryocytes, but did not cause significant changes in oxidative markers in erythrocytes. The definitive effects of these changes on health require further confirmation.