This article deals with the analysis of outbreak of mumps with the majority cases (88,7%) in groups of teenagers and young adults. The persons vaccinated with one dose of monovaccin against mumps showed the classic clinical symptoms. The tardy adress of infected individuals for treatment, in average 2,5 days after onset the illness, assist for dissemination of infection. The clinical diagnosis of mumps in 66,7% of cases was confirmed with the determination of specific IgM via ELISA. The population did not know the information about their vaccination, the majority did not know the doses and the terms of immunization, 45,2%-50,5% and 85%-92,7%, respective. The development of outbreak of mumps among teenagers and young adults was conditioned with the reducing of postvaccinal immunity after the immunization with one dose of vaccin 10-14 before. The high spread of dissemination of mumps was depend of the late izolation of infected persons. It is nessasary the supplementary measures for information the population about the imminization programmes for their active participation in the preventive actions.