Background: Roll-your-own (RYO) cigarettes are often substantially less expensive than factory made (FM) cigarettes, and appear to be increasing in popularity-perhaps because smokers seek out less expensive options to maintain their nicotine addiction. There is surprisingly little research available on the actual prevalence of RYO cigarette usage, and even less on the attributes of those who smoke RYO cigarettes. Objectives: This study has two objectives: (1) to compare the prevalence of RYO versus FM cigarette usage among adult smokers in Australia, Canada, the United Kingdom, and the United States; and (2) to compare the attributes of exclusive FM smokers, exclusive RYO smokers, and those who report ''mixed'' RYO and FM use. Design: The data were collected from the International Tobacco Control (ITC) Four Country Survey (ITC-4), a random digit dialed telephone survey of representative samples of over 9046 adult smokers from the following four countries: Australia (n = 2301), Canada (n = 2,206), the UK (n = 2400), and the USA (n = 2,139), surveyed between October and December 2002, and on 6075 smokers followed-up, on average, seven months later. Results: The prevalence of RYO cigarette usage varied widely across the four countries, with a low of 6.7% in the USA, to 28.4% in the UK. Exclusive use of RYO cigarettes was more common in the UK than in the other three countries. The use of RYO cigarettes was associated with having a lower annual income, male sex, younger average age, higher level of nicotine addiction, a stronger belief that RYO tobacco is less harmful compared to other forms of tobacco, and a more positive perception of tobacco use. Prevalence of RYO use was relatively stable within each of the four countries between the baseline and follow-up survey. RYO use was unrelated to quitting activity at follow-up, although mixed RYO users who had made a quit attempt were more likely to relapse than either exclusive FM or exclusive RYO smokers. Conclusions: Patterns of RYO use vary considerably across Australia, Canada, the USA, and the UK. RYO smokers are a heterogeneous group; however, the factors associated with RYO use appear to be the same across the four countries studied.