The aim of the paper was to determine the timeliness and level of primary immunization coverage against diphtheria, tetanus and whooping cough (pertussis), as well as the dropout rate in Montenegro in the cohort born from January 1 to December 31, 2006. Cross-sectional study was conducted in the period from October to December 2008. All immunization points in Montenegro were visited, and immunization records of entire cohort born in 2006 were reviewed. Timeliness of primary immunization coverage with DTP was 92.6% at the level of Montenegro, but in four out of 21 municipalities (19%) the timeliness of primary immunization coverage was less than 90%. After the additional activities on the vaccination of previously unvaccinated children, the primary immunization coverage with DTP reached the value of 98.1% at the level of Montenegro, and in all but two municipalities exceeded the value 95%. Dropout rate was 1.7% at the level of Montenegro, not exceeding the value of 5.5% in any municipality. In the cohort born during 2006, timely primary immunization with DTP was in 1/5 of Montenegrin municipalities, with the value less than 90%. Supplemental immunization activities related to unvaccinated children significantly increased the primary immunization coverage with DTP reaching the value of 95% at both the state and municipalities' level. Dropout rate was rather low both at the state and municipalities' level. Compared to routine administrative reporting on immunization coverage, surveys that include the review of immunization records after additional immunization activities provide more realistic rate of completeness and timeliness of primary immunization coverage.