Selection Criteria: Online electronic searches were performed in PubMed, Google Scholar, and the Cochrane Central Register of Controlled Trials to identify the studies to include in the review. The PubMed database was queried for [molar, third] and [asymptomatic]; [molar, third/surgery] and [epidemiologic studies]; [molar, third] and [pubmednotmedline]. The abstracts and subject headings from the resulting searches were manually reviewed to select those studies mentioning retention of asymptomatic third molars (M3s) and identifying the type of study done. The selected studies were reviewed manually for all references using PubMed. Additionally, Google Scholar was queried for [third molar asymptomatic]. The abstracts were manually reviewed by all 5 authors to select those studies reporting on retained M3s. The studies were included if they were an Englishlanguage publication, had a prospective study design, had more than 50 subjects, had recorded the number of subjects or M3s requiring extraction during the study period, and had a follow-up duration of 1 year or more. Additional criteria were subjects age 18 years or older, at least 1 M3 present at enrollment, and only asymptomatic M3s at enrollment. Key Study Factor: The primary predictor variable was the follow-up duration, recorded in years. The primary outcome variable was either the number of M3s removed during the follow-up period or the number of subjects who required 1 or more M3s removed during that period. Other study variables included subject age and the number of M3s or subjects present at the baseline examination. Main Outcome Measure: On average, 3% of previously asymptomatic third molars were removed every year, with more wisdom teeth removed as the patient gets older. Evaluations were made annually, up to a maximum of 18 years. Main Results: Seven studies were included in the systematic review, following consideration of 65 studies that were originally identified as possibly meeting the criteria set. The main reasons for exclusion were retrospective studies (22 studies), with a further 35 excluded because of insufficient follow-up period, outcomes were unclear, or the number of third molars at the start were unclear. The mean age at the start of the study was 25.2 years. The follow-up period ranged from 1 to 18 years. Overall, third molar removal varied from 5% to 64% of preliminary asymptomatic third molars, with a mean annual rate of removal of 3%. Conclusions: Given that there is an increasing likelihood of removal of previously asymptomatic third molars (which appears to increase with increasing age), such young adults should be advised of this potential outcome (together with an overview of the risks and indeed benefit of extraction verses retention).