The present study examined tobacco use, secondhand smoke exposure and related knowledge, attitudes and behaviors among Asian Americans in the Delaware Valley of Pennsylvania and New Jersey, and the relationship between acculturation and smoking, social influence patterns on smoking, and stages of change of smoking among Asian subgroups. Study sample was 1174 Chinese, Koreans, Vietnamese, Cambodians, and other Asians. Findings revealed mean age of initiation to be 18.3, 40% ever and 30% current users. Significant differences were reflected in smoking by gender, ethnicity, educational level, marital and employment status. While knowledge and attitudes about smoking and secondhand smoke were associated with these variables, ethnic pride and smoking status played significant roles. Fathers and brothers had greater social influence on young male smoking behavior; smoking friends had influence on both genders. Stages of change of smoking and acculturation impact on smoking varied with gender, age, and time living in the U.S. Findings provide comprehensive insights into tobacco use and related KAB among Asian Americans that reflect the need for developing culturally appropriate programs for this underserved population.