Inclusion criteria:  21 years or older Smoke five or more cigarettes per day for the past six months Biological confirmation of cigarette use: have an expired carbon monoxide (CO) level of more than 8 ppm and a urinary cotinine level of more than 100 ng per milliliter at screening  Exclusion criteria:  Intention to quit smoking in the next 30 days Weekly use of nicotine-containing products other than machine-manufactured combustible cigarettes Serious medical or psychiatric disorder precluding participation by study physician guidance Positive urine screening for illicit drugs other than cannabis or current substance use disorder Women who are pregnant, plan to become pregnant, or are breast-feeding Medical contraindications to receiving tobacco products