I have a Toshiba 1TB external drive formatted in NTFS. I works just fine on my Windows computer but won't show up at all on the two Macs I've tried. My Mac is running OS X 10.9.5 and I'm pretty sure the other one is running the same. I've tried looking in Disk Utility and it doesn't show up in there either. I can plug it into my PC and it works just fine. From what I've read, my Mac should be able to at least read the drive.