  We argue that the rate density of particle pair production $\Gamma$ in
background fields in conformal field theories is determined by the conformal
anomaly and related to anomalous trace of the energy-momentum tensor as $\Gamma
= (\pi/2) \langle T^\mu_{\ \mu}\rangle$ if the trace is positive (and $\Gamma =
0$ otherwise). This formula perfectly reproduces (presumably, non-Hawking)
radiation generated by static gravitational fields in the absence of an event
horizon via a new evaporation mechanism suggested recently. Our relation also
correctly describes the one-loop Schwinger pair creation in massless (scalar
and spinor) quantum electrodynamics. It also accurately points to the Savvidi
instability of the gluonic vacuum towards the formation of the chromomagnetic
condensate. Photon and neutrino pair production are also discussed.
