On the basis of analyses of differential CD44 expression patterns between primary brain tumours and brain metastases and the high incidence of CD44v detection in brain metastases formed by various types of systemic tumours, we further characterised CD44v proteins expressed in brain metastases studied previously with the antibodies specific for variant CD44v isoforms. The results demonstrate that CD44v expression in brain metastases is extremely heterogeneous. Generally, v5/v6 is homogeneously expressed in the cell populations, while up-regulated v7/v8 or v7-vl0 could be usually found in part of tumor cells, especially the ones close to necrosis, at tumour borders and with strong tendency of invasiveness. v7/vl0 could also be detected in microvascular endothelial cells of the tumoours. Our data thus describe multispectrum CD44v expression in the same tumours and even in individual tumour cells and suggest the necessity to use more than one antibodies in the study of CD44 expression in human malignancies.