Background: Impacted tooth is a tooth which is completely or partially unerupted and is positioned against another tooth, bone or soft tissue so that its further eruption is unlikely, described according to its anatomic position. The present study was conducted to assess prevalence of mandibular third molar impaction in adults. Materials & Methods: This study was conducted on 120 patients with impacted mandibular third molar. Prevalence and type of impaction was recorded. The position and level of the impacted teeth were assessed using the Pell and Gregory classification. The present study was conducted to assess prevalence of mandibular third molar impaction in adults. Results: Out of 120 patients, males were 65 and females were 55. Common type of impaction was mesio- angular seen in 58%, disto- angular in 24%, horizontal in 12% and vertical in 6%. The difference was significant (P< 0.05). Level of third molar was level A in 20%, level B in 65% and level C in 15%. Ramus relationship was class I in 18%, class II in 54% and class III in 28%. The difference was significant (P< 0.05). Conclusion: Authors found that mesio- angular was the most common type of impaction and level B and class II was most common level and depth of impaction among adults. Key words: Impaction, Third molar, Ramus relationship