Purpose: Only a few studies have presented long-term trends in the prevalence of periodontitis and periodontal treatment needs. The aim of this study was to report the changes in periodontal treatment needs of an adult population in Ljubljana, Slovenia, over a 30-year period. Materials and Methods: This study included 88 45- to 95-year-old subjects who had attended the previous three studies 10, 20 and 30 years ago. We used the CPITN for assessing periodontal treatment needs, as the same index had been used in the previous three studies. Results: None of the examined subjects had healthy periodontal tissues, all needed oral hygiene instruction, 96.6% needed scaling and root planing as well as oral hygiene instruction, 47.7% needed complex periodontal treatment as well as oral hygiene instruction plus scaling and root planing. Periodontal treatment needs in Ljubljana adults increased in thirty years in the total study population as well as among 45- to 65-year-olds. Conclusion: Periodontal treatment needs in an adult population of Ljubljana are high and have increased in the last thirty years. More effective primary and secondary preventive measures are needed to decrease the prevalence of periodontal disease and periodontal treatment needs in the adult population of Ljubljana, Slovenia. Keywords: periodontal disease, periodontal treatment needs, Ljubljana citizens