Background: Under five years deaths can be prevented through optimal use of currently existingrnvaccines. In 2012 nearly one in five infants missed the basic vaccines they need to stay healthyrnglobally, and majority of the children missed in sub Saharan Africa including Ethiopia. Missedrnopportunities are an obstacle to raise immunization coverage among children and leading highrninfant morbidity and mortality.rnObjective: The objective of this study was to determine magnitude and the related factors forrnmissed opportunity of routine immunization of infants under one year age in Wolikite health centerrnGurage zone, southern regional state, Ethiopia, May 2015rnMethodology: The study was health facility based cross sectional design. Exit interview wasrnadministered for mothers who had under one infants and who came for any services for their infantrnat Wolikte health center, Gurage zone from March 27- April 22, 2015 using standard world healthrnorganization missed opportunity tool in the context of Ethiopia routine immunization schedule. Thernsample size was calculated by using single proportion formula with 95% confidence interval and arntotal of 346 mothers were interviewed.rnResult:The magnitude of missed opportunity for the study was 49.1% and the major vaccines withrnhigh missed opportunity were oral polio vaccine o (37.9), (Bacille Calmette Guerin 35), andrnmeasles (31.1) the major reason for immunization for missed vaccines was due to absence ofrnadequate number of children to conduct immunization sessions which was around 81.2% amongrnchildren who had missed opportunities. Age of children, stock out experience of care takers,rnknowledge of contact time and purpose of visit to health facility were independently associatedrnfactors for children missed opportunity of immunization.rnConclusion: The overall magnitude of missed opportunity for the routine immunization is highrninfluencing the success of immunization services. The major vaccines which highly contributed forrnthe prevalence of immunization missed opportunity were measles, and Bacille Calmette Guerin andrnoral polio vaccine.