A survey was conducted in 2006 to assess the coverage and timeliness of the birth dose of hepatitis B vaccine (HepB(1)) and related influences among children in rural areas of Guangxi, Guizhou, Tibet, and Shaanxi provinces, People's Republic of China. A total of 3,390 children born in 2004 were surveyed in four counties in each province, where a project to strengthen routine immunization is being implemented by the China Ministry of Health, supported by the United National Children's Fund. Two-stage stratified cluster sampling was undertaken to select those surveyed. A questionnaire was administered to parents or guardians and vaccination records were assessed. HepB(1) administration was timely for 31.6% of the sample. Timeliness of HepB(1) for children delivered at home (13%) was lower than for children born at county-level or higher facilities (54%) (odds ratio [OR] = 6.52, (95% confidence interval [CI] = 5.29-8.04, P < 10 (-3)), at township hospitals (49%, OR = 7.14, 95% CI = 5.68-8.98, P < 10 (-3)), or private clinics (59%, OR = 5.64, 95% CI = 3.68-8.64, P < 10 (-3)). Children of Tibetan (24.8%, OR = 0.16, 95% CI = 0.12-0.21, P < 10 (-4)), Zhuang (27.8%, OR = 0.73, 95% CI = 0.57-0.94, P < 0.02) or Meng, Miao, and Hui ethnicity (14.2%, OR = 0.36, 95% CI = 0.29-0.45, P < 10 (-4)) were less likely than children of Han ethnicity (33.2%) to have received a timely birth dose. Children lacking vaccination registration cards (OR = 0.64, 95% CI = 0.51-0.80, P < 10 (-4)) and children whose parents or guardians did not know the importance of timely HepB immunization (OR = 0.62, 95% CI = 0.46-0.84, P < 10 (-2)) were also less likely to have received a timely birth dose. Parental knowledge and prioritization of birth-dosing was low among children who did not receive it. The timeliness of HepB(1) should improve with increasing rates of hospital delivery, training of birth attendants, increasing staff and community awareness of the importance of the birth dose, and by focusing on vulnerable groups.