E-cigarettes may benefit public health if they are effective for smoking cessation. Evidence suggests that the frequency of e-cigarette use is likely an important predicator of smoking cessation success, so we examined the associations between frequency of e-cigarette use and smoking reduction and cessation in an Australian population sample of past year adult smokers. [...] Daily, but not occasional, e-cigarette users were more likely to quit or reduce smoking cigarettes than Australian smokers who did not use e-cigarettes.