Leiomyoma is the most common benign neoplasm in the uterus and stomach but is rare in the oral cavity. There were only 5 oral cases in a series of 7748 leiomyomas of all sites. Benign smooth muscle neoplasms are classified into leiomyoma (solid leiomyoma), angiomyoma (vascular leiomyoma) and epithelioid leiomyoma (leiomyoblastoma). 6 cases diagnosed as leiomyoma were retrieved from the files of two oral biopsy services over the past 25 years. A light microscopic study including trichrome and phosphotungstic acid haematoxylin (PTAH) stains, and an immunohistochemical study with the following markers: desmin, muscle specific actin, myoglobin, vimentin, S-100 protein, neuron-specific enolase, factor VIII and Ulex europeus were done with suitable controls. The haematoxylin and eosin and Masson's trichrome stains supported a diagnosis of leiomyoma in all 6 cases but PTAH was positive in only 3 of them. The immunohistochemical study confirmed the diagnosis of leiomyoma in 3 cases. The other 3 were identified as granular cell tumour, myofibroma and neurofibroma, respectively. The review of the literature contributed the following data: mean age was 41 and median age 39 in 134/142 patients. A male sex prevalence 72/137 patients (54.0%) was noted. The lips were the most common site with 39 cases (27.46%) followed by the tongue 26 (18.30%), cheeks and palate 22 (15.49%), gingiva 12 (8.45%), and mandible 8 (5.63%). Prognosis of oral leiomyomas is excellent. Immunohistochemistry is a precise and reliable method for definitive diagnosis of oral leiomyoma.