BACKGROUND: Haramonting leaves have a large antioxidant activity as inhibitors oxidation and form non-free radical compounds that are not reactive and relatively stable. Electronic smoking is a choice who slowly want to quit conventional smoking.AIM: This research aimed to determine the effect of ethanol extract on hard mounting leaves on leukocyte counts and histology Pulmo on male mice exposed to an electronic cigarette.METHODS: The samples used in this study were healthy male mice aged 8-11 weeks and weight of 25-30 g as many as 25 individuals and ethanol extracts of hard mounting leaves with a dose of 100 mg/kgBW, 200 mg/kgBW and 300 mg/kgBW. Blood tests were carried out at the Health Laboratory of North Sumatra Office, and the preparation of Pulmo histology was carried out at the Pathology and Anatomy Laboratory of Adam Malik General Hospital MedanRESULT: There were significant differences between the control group and all of the treatment groups in the number of lymphocytes, neutrophils, basophils and eosinophils. There was a tendency that electronic cigarette smoke could cause damage to pulmo tissue.CONCLUSION: The results of this study indicate that the ethanol extract of hard mounting leaves could help the immune system in mice exposed to an electronic cigarette.