The code below is from Rhino IronPython Help and userinterface.py (V6), with ShowOpenDialog in place of ShowDialog in the latter.
When the script is run in V5, multiple files can be selected and fd.FileNames contains all the paths and file names.
When run in V6, only a single file can be selected, but fd.FileNames contains an empty array.
import Rhino import rhinoscriptsyntax as rs def openFileNames(title=None, filter=None, folder=None, filename=None, extension=None): fd = Rhino.UI.OpenFileDialog() if title: fd.Title = title if filter: fd.Filter = filter if folder: fd.InitialDirectory = folder if filename: fd.FileName = filename if extension: fd.DefaultExt = extension fd.MultiSelect = True if fd.ShowOpenDialog(): return fd.FileNames return  filenames = openFileNames("Open", "Text Files (*.txt)|*.txt|All Files (*.*)|*.*||") for filename in filenames: print filename