  Let $d(u,v)$ denote the distance between two distinct vertices of a connected
graph $G$, and $\diam(G)$ be the diameter of $G$. A radio labeling $c$ of $G$
is an assignment of positive integers to the vertices of $G$ satisfying
$d(u,v)+|c(u)-c(v)|\geq \diam(G) + 1.$ The maximum integer in the range of the
labeling is its span. The radio number of $G$, $rn(G)$, is the minimum possible
span. The family of gear graphs of order $n$, $G_n$, consists of planar graphs
with $2n+1$ vertices and $3n$ edges. We prove that the radio number of the
$n$-gear is $4n+2$.
