Background & objective: Most of the vaccine-preventable diseases have shown a decline with the advent of National immunization schedule but Diphtheria is still present in some region of India. The purpose of this study is to diagnose outbreak cases of Diphtheria. Material and Method: This study was performed during June 2016 to October 2016 at the Bacteriology Laboratory of Microbiology Department, Civil Hospital, Ahmedabad-as IDSP state reference laboratory. Two throat swabs received from each suspected patient with detailed clinical and immunization history. One swab was inoculated in selective and enrichment culture media while another was used for microscopic examination for isolation of Corynebacterium diphtheriae. Result: Out of total 126 samples Corynebacterium diphtheriae was isolated in 10 samples. Among 10 cases, 7 were dead, so case fatality rate is 70%. Out of 7 deaths, 4 patients belonged to under 5, while 3 belonged to 6-12 years of age group. Interpretation & Conclusion: The majority of cases are reported from children who were non-immunized or partially immunized against Diphtheria. Persistence or resurgence of Diphtheria is mainly due to low coverage of primary immunization as well as booster doses and inaccessible areas. Targeted immunization coverage is required specifically in inaccessible areas.