The Urban Basic Services (UBS) programme was launched in some of the urban slums in the major cities of India in the year 1986. The main objective of the Urban Basic Services (UBS) Program is to improve and upgrade the quality of life of the urban poor, particularly the women and children. The major thrust area under the UBS programme includes child survival and development, learning opportunities for women and children, water and sanitation, and community organization. The present study attempts to find out the impact of the UBS Program in terms of the immunization coverage carried out in slums covered by UBS and comparing it with non-UBS slums using the 30-cIuster sampling technique as suggested by WHO. The percentage of fully immunized children was higher (16.2%) in the UBS slums compared to 10.9% in non-UBS slums. The immunization coverage of children was slightly better in the UBS slums for BCG, DPT and Oral Polio Vaccines, while for measles it was 18.6% in UBS slums and 11.9% in non-UBS slums. The dropout rates for I to III doses of DPT was much higher (36.4%) in non-UBS slums as compared to 28% in UBS slums. The availability of immunization cards was found to be higher in both mothers (16.7%) and children (22.4%) in UBS slums compared to the non-UBS ones (5.2% and 8.6% respectively). The slums thus covered under the UBS program have done marginally better in immunization but it appears that to assess the overall impact of UBS, all the components of services and not merely immunization should be assessed.