The study aimed to assess the determinants of immunization coverage in 12-23-month-old children born in 1997 and living in Gansu Province in West China. The World Health Organization's cluster sampling technique was used. Information was gathered by face-to-face interviews with caregivers and from immunization records. Bacille Calmette Guerin (BCG), Polio and Diphtheria, Tetanus, Pertussis (DTP) coverage at 3 months was 51.2%. At 8 and 12 months, including the Measles Vaccine, coverage was 71.3 and 86.0%, respectively. The variables associated with delay at 12 months were: low socio-economic level, low number of sources of information on vaccination and delayed immunization at 3 months. Improved immunization coverage could be achieved by improving access and delivery to poor and remote areas and by awarding incentives to providers at primary care level.