  Coexistence of the "metallic-like" in-plane and the "semiconducting-like"
out-of-plane (caxis) dc conductivities ({\sigma}c), generating a huge
anisotropy in the underdoped hightemperature cuprate superconductors (HTCS),
defies our current understanding of metal. In this report we present an
intrinsic doping dependence of {\sigma}c. We find that the {\sigma}c for the
underdoped HTCS is universally scaled to the {\sigma}c at the optimal
doped-hole concentration. The universal scaling behavior suggests that there
are three intrinsic processes contribute to {\sigma}c: (i) the
doping-dependent-activated gap; (ii) the exponential doping dependences and
(iii) the tunneling between adjacent CuO2 block layers. They are the essential
underlying characteristics of the c-axis transport for all HTCSs.
