¹Muğla Sıtkı Koçman University, Vocational School of Health Services, Medical Services and Techniques, Muğla, Turkey DOI : 10.29228/jrp.2022.00 Remifentanil is an analgesic used in clinical settings. However, its potential genotoxic effects on lymphocytes have not been extensively investigated. This research aimed to assess the dose-dependent impact of remifentanil on micronucleus formation in healthy human lymphocytes after exposure of 24 and 48 hours, comparing them with spontaneous and positive controls. Lymphocytes from healthy individuals were exposed to remifentanil at concentrations of 50, 150, 250, and 350 μg/mL for 24 and 48 hours. Micronucleus formation incidence was evaluated and compared with both spontaneous control and positive control groups. Remifentanil elevated the formation of micronucleus in a dose dependent manner as compared to the spontaneous control values, however, this increse was not significant statistically. This increase was significant at only the highest (350 μg/mL) concentration. Micronucleus (MN) frequency was statistically significant at only the 350 μg/mL dose of remifentanil when compared with the spontaneous. The value of cell proliferation index (CPI) was not decreased by remifentanil when compared to spontaneous control. Decrease in CPI values provide information about the genotoxicity of the doses. Evaluation of remifentanil research should extend beyond in vitro methods to include in vivo approaches applied to individuals with frequent exposure, particularly concerning chromosomal abnormalities. Keywords : Micronucleus assay; remifentanil; lymphocyte culture; toxicity