Although tumour cell nuclei are important histological structures for grading of astrocytomas according to the WHO-classification of brain tumours, there is no reported morphometric study of astrocytomas which describes quantitatively the four main morphologic criteria of tumour cell nuclei: size, shape, texture (densitometric characteristics) and spatial relationships between the nuclei (topometric analysis). Using a set of morphometric parameters describing these criteria as well as the Ki67-proliferation index, 74 astrocytomas from 74 patients were studied by means of a digital image analysis system. The objective of the study was to test, if these morphometric parameters were sufficient for statistical discrimination between pilocytic astrocytomas WHO-grade I, astrocytomas grade II and anaplastic astrocytomas grade III. Our results showed a correct reclassification of 97.3% (72/74) of the cases with respect to the tumour grade by means of cross-validated discriminant analysis. Morphometric parameters characterizing nuclear shape (shape factors, Fourier-amplitudes) showed the most prominent differences between the three groups of cases, followed by topometric parameters (number of neighbours per nucleus, distances between the nuclei). Less pronounced differences between the tumour grades were found for parameters characterizing nuclear size, nuclear texture and the Ki67-proliferation index. In conclusion, the present morphometric procedure provided good discrimination between the tumour grades, supporting the view that histomorphometry of tumour cell nuclei could be a valuable tool for grading of astrocytomas.