Cell kinetic parameters were measured in four cases of meningioma showing regrowth. The cell cycle time (Tc) and tumor doubling time (Td) were established by histological evaluation of the biopsy specimens and calculation of the growth curve based on computed tomography (CT)/magnetic resonance (MR) images. MIB-1 mouse monoclonal antibody, which recognizes an epitope of the Ki-67 antigen, was used to establish the MIB-1 staining index (SI) (MIB-1-positive nuclei/5000 tumor cells) for each tumor. The changes in tumor volume were calculated from CT/MR images, and the Td was estimated from the growth curve. The Tc was calculated using Steel's formula from the MIB-1 SI and tumor volume. MIB-1 SI varied from 0.0055 to 0.0468, Td from 270 to 1429 days, and Tc from 10.4 to 15.9 days. Furthermore, the potential doubling time (Tp) was calculated using the corresponding Tc and MIB-1 SI (growth fraction) for the four cases; these values varied from 197 to 1645 days and were very close to the Td values. This method of evaluation of tumor Tc and calculation of Tp may be useful for predicting the postoperative course in meningiomas.