This book covers the basic and advance cytological techniques in diagnosing various lesions in relation to oral cavity. These oral lesions commonly include microbial infections, reactive and immune reactions, inflammatory conditions, premalignant and malignant lesions and may progress to several life- threatening conditions. Early detection of oral lesions remains the best way to ensure patient survival and improved quality of life. Cytology being a non-invasive, inexpensive and less time consuming technique acts as useful marker in the early detection of oral lesions. Oral cytology is becoming increasingly important in the early diagnosis of oral cancers, as a procedure for obtaining cell samples that can then be analysed by sophisticated diagnostic techniques such as cytomorphometry, DNA analysis, and molecular analyses.The introduction of advanced cytologic methods has made the interpretation of findings far more reliable than earlier. It is an adjunct to biopsy in such cases and makes the screening of cancer easy. In this manner, oral cytology can be considered as a valuable tool in evaluating oral lesions.