  In this paper, a characterization for inner uniformity of bounded domains in
Euclidean $n$-space $\mathbb{R}^n$, $n\ge 2$, in terms of the Gromov
hyperbolicity is established, as well as the quasisymmetry of the natural
mappings between Gromov boundaries and inner metric boundaries of these
domains. In particular, our results show that the answer to a related question,
raised by Bonk, Heinonen and Koskela in 2001, is affirmative.
