Introduction: Inpatient medical settings offer an opportunistic environment for initiating smoking cessation interventions to patients reflecting on their health. Current evidence has shown the superior efficacy of varenicline tartrate (VT) for smoking cessation compared with other tobacco cessation therapies; however, recent evidence also has highlighted concerns about the safety and tolerability of VT. Given these apprehensions, we aimed to evaluate the safety and effectiveness of VT plus quitlinecounseling compared to quitline-counseling alone in the inpatient medical setting. Methods: Adult patients (n = 392, 20-75 years) admitted with a smoking-related illnesses to 3 hospitals were randomized to receive either 12 weeks of varenicline tartrate (titrated from 0.5 mg daily to 1 mg twice daily) plus quitline-counseling (VT+C), (n = 196) or quitline-counseling alone (n = 196). Results: VT was well tolerated in the inpatient setting among subjects admitted with acute smoking-related illnesses (mean age 52.8 ± 2.89 and 53.7 ± 2.77 years in the VT+C and counseling alone groups, respectively). The most common self-reported adverse event during the 12-week treatment phase was nausea (16.3% in the VT+C group compared with 1.5% in the counseling alone group). Thirteen deaths occurred during the study period (n = 6 were in the VT+C arm compared with n = 7 in the counseling alone arm). All of these subjects had known comorbidities or developed underlying comorbidities. Conclusions: VT appears to be a safe and well-tolerated opportunistic treatment for inpatient smokers who have related chronic disease. Based on the proven efficacy of varenicline from outpatient studies and our recent inpatient evidence, we suggest it be considered as part of standard care in the hospital setting.