Park EY, Park E, Jeong BY, et al. - Since it remains unknown if the machine-smoked nicotine yield of usual brand of cigarette smoked is related to the likelihood of success of quit attempts, researchers undertook this prospective analysis in the Republic of Korea, to evaluate this relationship. This study included 13,176 of 16,808 male smokers registered for the Quitline, who were > 19 years of age and provided the required data. The definition of ultra-low nicotine yield was ≤ 0.1 mg machine-smoked nicotine yield per cigarette, and that of higher nicotine yield was > 0.1 mg machine-smoked nicotine yield. In the ultra-low nicotine yield vs higher nicotine yield groups, the continuous abstinence rates were estimated to be 40.7% vs 34.6% at 1 month 22.7% vs 18.8% at 6 months, and 19.5% vs 16.6% at 1 year, respectively. The probability of quitting successfully was more among male smokers who used the Korean Quitline if they smoked ultra-low nicotine yield cigarettes vs if they used higher nicotine yield cigarettes.