ABSTRACT: Objective:To evaluate the association between contraceptive knowledge and type of method used. Methods:We analyzed data from a cross-sectional study of sexually active women in Hanoi, Vietnam, not desiring pregnancy. We used linear and logistic regression to evaluate contraceptive knowledge of users of the intrauterine device (IUD), combination oral contraception (COC) and male condoms. We measured contraceptive knowledge with seven questions on relative effectiveness of methods, reversibility, covert use, contraindications and side effects. Results:Respondents used IUD (n = 128), COC (n = 126) or condoms (n = 167). Summary knowledge scores did not differ by current type of method used. Only one knowledge domain, contraceptive effectiveness, varied by method. Compared to condom users, IUD users had higher odds of correctly identifying the IUD as more effective than COC, condoms and withdrawal (adjusted odds ratio [aOR], 4.8; 95% confidence interval [CI], 2.7-8.3). Higher proportions of condom users (49.7%) mistakenly identified condoms as the most effective of listed methods compared to IUD (20.3%) and COC users (23.0%). On the other hand, IUD and COC users had lower odds (aOR, 0.5; 95% CI, 0.2-1.0 and aOR, 0.3; 95% CI, 0.1-0.6, respectively) of identifying consistent condom use as better for pregnancy prevention than other practices (e.g., withdrawal and postcoital douching). Conclusions:IUD users more often recognized that the IUD is highly effective while condom users appeared to overestimate condom effectiveness. Contraceptive counseling should ensure that women understand the relative effectiveness of methods. We found no evidence that other types of contraceptive knowledge differed by type of method used. Implications:Knowledge of contraceptive effectiveness was the sole difference detected in contraceptive knowledge between women in Hanoi, Vietnam, using the IUD, COC or male condoms.