Background : Basic immunisation is an effort to give immunity or to prevent several diseases such as measles, polio, diphtheria, pertusiss, tetanus, TBC, and hepatitis. Karangdowo district is one of areas which immunisation prevented diseases are still found, so immunisation has big role to decrease the diseases risk. Ironically, there are still some people who choose not to give immunization for their children. Until now the etiology of immunization prevented disease are still unknown. In order to know the etiology of immunization prevented disease in Karangdowo district it is required to understand the factors which influence mothers’ perception. Method : This study use qualitative approach with descriptive design. Data were collected through deep interview from ten respondent recruited using purposive select technique. The data were analysed using qualitative analysis method Result : Using depth interview, it is found that there are four things which influence mothers’ perception such as strong motivation from the mother and environment, obstacles in organizing the basic immunization, mothers’ sense of responsibility and mother persistency not to do immunization. Conclusion : The success rate of basic immunizations depends on mother motivation, obstacles in organizing the basic immunization and mothers’ sense of responsibility to do immunization. Meanwhile the failure rate of basic immunization were influenced by mothers’ persistency not to do immunization.