Syndecans are a family of cell-surface heparan sulphate proteoglycans which are involved in cell-matrix interactions and growth factor binding. Syndecan-1 binds basic fibroblast growth factor (bFGF) and several components of the extracellular matrix. Syndecan-1 expression is induced during keratinocyte differentiation and reduced during the formation of squamous cell carcinomas (SCCs). The purpose of this study was to examine the association of syndecan-1 expression with prognostic factors and clinical outcome in SCC of the head and neck. Frozen sections of 29 primary SCCs were analysed for syndecan-1 expression using immunohistochemical methods. Intermediate or strong staining for syndecan-1 was associated with a smaller primary tumour size (P = 0.0005) and higher histological grade of differentiation (P = 0.006) than negative or weakly positive staining. In a univariate analysis, syndecan-1-positive tumours were associated with higher overall (P = 0.001) and recurrence-free survival (P = 0.003) than those tumours with no or little syndecan-1 expression. The results suggest that syndecan-1 could be an important prognostic factor of SCC of the head and neck. Further studies on the prognostic significance of syndecan-1 expression in SCCs are warranted.