The purpose of this study is to develop and then test the feasibility, acceptability, and preliminary effect of a bidirectional text message smoking cessation intervention among Vietnamese smokers in Hanoi, Vietnam. The specific aim are: 1) To develop a smoking cessation text message library among Vietnamese smokers; 2) To evaluate message preferences, and the feasibility and acceptability of the bidirectional text message smoking cessation intervention; and 3) To assess the preliminary effect of a bidirectional mobile phone text message intervention on biochemically validated smoking abstinence.