  In this work we explore experimental signatures of fractional topological
insulators in three dimensions. These are states of matter with a fully gapped
bulk that host exotic gapless surface states and fractionally charged
quasiparticles. They are partially characterized by a non-trivial
magneto-electric response while preserving time reversal. We describe how these
phases appear in a variety of probes including photoemmission, tunneling, and
quantum oscillations. We also discuss the effects of doping and proximate
superconductivity. We argue that despite our current theoretical inability to
predict materials where such phases will realized, they should be relatively
easy to detect experimentally.
