Primary cutaneous B-cell lymphomas (CBCLs) represent a rare, but distinct group of B-cell neoplasms with a different clinical behaviour to B-cell lymphomas secondarily involving the skin. Fas-Fas ligand (Fasl) expression was investigated in a group of primary and secondary CBCLs to gain an insight into the putative role of these apoptotic molecules in the clinical behaviour of these lymphomas. Frozen and paraffin sections from 32 patients with a CBCL were investigated for Fas and Fasl expression, using immunohistochemistry. This group included 24 primary CBCLs [14 primary cutaneous follicle centre cell lymphomas (PCFCCLs), six primary cutaneous large B-cell lymphomas (PCLBCLs) on the leg, and four primary cutaneous immunocytomas] and eight secondary CBCLs. The results were correlated with follow-up data, bcl-2, and ICAM-1 expression. High Fas expression and absent or low Fasl expression were detected in the vast majority of PCFCCLs and immunocytomas. The group of PCLBCLs on the leg, which have an intermediate prognosis, showed variable results with relatively higher Fasl expression. The highest Fasl expression was found in the more aggressive secondary CBCLs whereas in this group, Fas was undetectable in five of eight cases. Statistical analysis showed that Fas and ICAM-1 expression was strongly related to a favourable prognosis, whereas expression of Fasl and bcl-2 was related to a very poor prognosis. Although only type of CBCL and age, but not Fas, Fasl, bcl-2, and ICAM-1 expression, proved independent prognostic parameters using multivariate analysis, the results of this study suggest that differences in the expression of Fas and Fasl, as well as bcl-2 and ICAM-1, contribute to the differences in clinical behaviour between these different types of CBCL.