Recruiting Diverse Smokers: Enrollment Yields and Cost.

To help tobacco control research better include vulnerable populations, we sought to identify effective ways to recruit diverse smokers. In 2014-2015, we recruited 2149 adult cigarette smokers in California and North Carolina, United States, to participate in a randomized trial of pictorial cigarette pack warnings. The most effective means of recruiting smokers were the classified advertising website Craigslist (28% of participants), word of mouth (23%), Facebook (16%), and flyers or postcards (14%). Low-income and African American smokers were more likely to respond to interpersonal contact (including staff in-person recruitment and word of mouth) than were high-income and non-African American smokers (all < 0.05). Hispanic and gay, lesbian, and bisexual smokers were more likely to be recruited by Craigslist than non-Hispanic and straight smokers (both < 0.05). Of the recruitment methods requiring cost, the cheapest was Craigslist ($3-7 per smoker). The most expensive methods were newspaper ads in California ($375 per smoker) and staff in-person recruiting in North Carolina ($180 per smoker). Successfully recruiting diverse smokers requires using multiple methods including interpersonal, online, and other media. Craigslist and word of mouth are especially useful and low-cost ways to recruit diverse smokers.