  We examine the possibility of positive spectral index of the power spectrum
of the primordial tensor perturbation produced during inflation in the light of
the detection of the B-mode polarization by the BICEP2 collaboration. We find a
blue tilt is in general possible when the slow-roll parameter decays rapidly.
We present two known examples in which a positive spectral index for the tensor
power spectrum can be obtained. We also briefly discuss other consistency tests
for further studies on inflationary dynamics.
