Background: To determine the knowledge, attitude and practices about immunization among respondents of children aged 12-23 months.Methods: A total of 510 respondents were interviewed in the urban slums of Lucknow district of India, using 30 cluster sampling technique from January 2005 to April 2005. A pre-tested structured questionnaire was used to elicit the information about the knowledge, attitude and practices of the respondents regarding immunization. Results: Knowledge regarding the disease prevented, number of doses and correct age of administration of BCG was highest among all the categories of respondents. The paramedical worker was the main source of information to the respondents of completely (52.0%) and partially immunized (48.5%) children while community leaders for unimmunized children. Those availing private facilities were more completely immunized, as compared to the government facilities. 55.8% of those who took 20 minutes to reach the immunization site were completely immunized as compared to 64.1% of those who took more than 20 minutes.Conclusion: Considering the incomplete knowledge, and inappropriate practices of the people, the policy makers and medical professionals require Herculean efforts to raise the knowledge and to break the old beliefs of the people