HI! You can do it like this: vtkDataSet::GetNumberOfCells(); for(cellId = 0,cellId<number,cellId++) { vtkCell *cell = vtkDataSet::GetCell(cellID); if(cell->GetCellType() == VTK_TRIANGLE) nTriangle ++; } It is slow possibly,but I can not find other method! Regards, beelin beelin at sohu.com 2006-07-11