We report on a case of malignant basal cell carcinoma of the prostate combined with a poorly differentiated conventional adenocarcinoma, infiltrating bilaterally the seminal vesicles and with lymph-node and distant metastases. Basal cell carcinoma represented the prevalent component of the tumour (80%), showed high mitotic activity, extensive perineural infiltration and vascular invasion and was immunoreactive for basal cell related antigens (high molecular weight cytokeratins 34betaE12 and p63). Our data confirm previous observations that basal cell carcinoma represents aggressive tumour with an adverse clinical outcome.