Introduction 14 20 9 13 16 17 20 21 15 9 13 16 17 21 2 1 3 4 6 8 11 12 18 19 12 12 2 11 15 1 3 4 8 11 13 16 19 21 Materials and methods between 1995 and 2004 Location locations 9 10 Statistical analysis All data were stored on a personal computer and analyzed using commercially available statistical software (SPSS version 12.0, SPSS Inc.). Chi-squired analysis was used to compare the MIB-1 staining index to characteristics of patients with meningioma. All variables were included in a logistic regression model to determine which variables were independently associated with a high MIB-1 staining index (≥3.0). Significance was judged at a value of p<0.05 for all analyses. Results 1 3 11 Table 1 Characteristics and MIB-1 staining index in 342 meningiomas   MIB-1 staining index (%)   Factor <3.0 ≥3.0 P Value Age (years)   0.937 -49 65 24  50- 72 32  60- 79 34  70- 26 10  Sex (male/female) 46/196 43/57 0.0001 Recurrence (yes/no) 14/228 34/66 0.0001 Symptomatic (yes/no) 133/109 70/30 0.013 Skull base (yes/no) 119/123 38/62 0.059 3   0.014 -9.9 113 37  10- 53 15  20- 76 48  Multiple (yes/no) 15/227 9/91 0.244 Edema (yes/no) 82/160 54/46 0.001 Calcification (yes/no) 97/145 20/80 0.0001 Total 242 100  MIB-1 staining index in 56 of 296 grade I meningiomas was 3.0; that in 27 of 28 grade II; and that in 17 of 18 grade III, respectively 2 . Table 2 Histological subtypes and MIB-1 staining index of 342 meningiomas Subtype MIB-1 staining index (%) Total <3.0 ≥3.0 Grade I    Meningothelial  106 28 134 Fibrous 67 13 80 Transitional 43 13 56 Psammomatous 6 0 6 Angiomatous 13 2 15 Microcystic 1 0 1 Secretory 1 0 1 Lymphoplasmacyte-rich 1 0 1 Metaplastic 2 0 2 240 56 296 Grade II    Atypical 1 26 27 Chordoid 0 1 1 1 27 28 Grade III    Rhabdoid 0 1 1 Papillary 1 1 2 Anaplastic 0 15 15 1 17 18 Total 242 100 342 3 Table 3 Logistic regression analysis for factors independently related to MIB-1 staining index Factor Odds ratio 95%CI P Value Age 1.109 0.841–1.461 0.464 Sex 2.374 1.336–4.219 0.003 Recurrence 7.574 3.558–16.124 0.0001 Symptomatic 1.468 0.774–2.784 0.240 Skull base 0.540 0.305–0.956 0.035 Volume 1.332 0.944–1.879 0.103 Multiple 1.027 0.398–2.651 0.957 Edema 1.508 0.838–2.711 0.170 Calcification 0.498 0.278–0.892 0.019 Discussion We analyzed the relationship of the MIB-1 staining indices to the characteristics of 342 consecutive patients with meningioma surgically removed between 1995 and 2004 by logistic regression analysis. Logistic regression analysis demonstrated that male (odds ratio [OR], 2.374, p=0.003), recurrence (OR, 7.574, p=0.0001), skull base (OR, 0.540, p=0.035), calcification (OR, 0.498, p=0.019) were independent risk factors for a high MIB-1 staining index (≥ 3.0); age, symptomatic, volume, multiple, and edema were not. 11 13 21 1 12 15 19 10 11 1 11 19 20 15 19 9 16 15 13 16 21 1 4 4 15 9 13 16 5 15 In conclusion, male, recurrence, non-skull base, absence of calcification are independent risk factors for a high proliferative potential. These should be taken into consideration when managing meningiomas.