In order to elucidate the influence of surgical intervention on cell kinetics, we investigated the DNA ploidy pattern and mitotic index in two patients with metastatic pulmonary meningioma more than 10 years after the first operation for primary brain lesions. The first patient, with hemangiopericytomatous meningioma, showed a diploid pattern in all resected specimens and intrathoracic metastases obtained at autopsy, and also showed a constant mitotic indices throughout the clinical course. The second patient, with meningothelial meningioma, also showed a diploid pattern and constant mitotic indices throughout the clinical course. There was no difference in the two parameters between this second patient and 5 non-metastatic control cases. In conclusion, there was no positive correlation between these two parameters and the acceleration of tumor growth detected at every surgical intervention.