To evaluate the expression patterns of apoptosis-related proteins, including Fas, Fas-ligand (FasL), caspase-3 and Bcl-2, in various cellular components of ameloblastomas, 39 cases of ameloblastoma were examined using immunohistochemistry. The staining intensity of the antigens in the 4 types of tumour cellular component, peripheral basal cells of tumour nests, central stellate reticulum-like cells, and foci of squamous and granular cells, was scored using a semi-quantitative scale, and comparisons were made by statistical analysis. Expression of Fas, FasL and caspase-3 was detected in the majority of cases, with a similar pattern of strong staining in the foci of squamous metaplasia and granular cells usually situated in the central area of tumour islands. In contrast, expression of Bcl-2 was predominantly seen in the peripheral basal cell layer. There were significant differences in the staining intensity of Fas, caspase-3 and Bcl-2 among the 4 types of tumour cell. The differential expression of apoptosis-related proteins in various cellular components of ameloblastomas, with pro-apoptotic proteins, Fas, FasL and caspase-3 being closely associated with squamous metaplasia and granular transformation of the tumour cells, suggests that Fas/FasL-induced apoptotic cell death may play a role in the disposal of terminally differentiated or degenerative tumour cells in ameloblastomas.