Abstract. A subset
$W$ of the vertex set of a graph
$G$ is called a resolving set of
$G$ if for every pair of distinct vertices
$u,\,v$, of
$G$, there is
$w\,\in \,W$ such that the distance of
$w$ and
$u$ is different from the distance of
$w$ and
$v$. The cardinality of a smallest resolving set is called the metric dimension of
$G$, denoted by
$\dim\left( G \right)$. The circulant graph
${{C}_{n}}\left( 1,\,2,\,.\,.\,.\,,\,t \right)$ consists of the vertices
${{v}_{0}},\,{{v}_{1\,}},\,.\,.\,.\,,{{v}_{n\,-\,1}}$ and the edges
${{v}_{i}}{{v}_{i\,+\,j}}$, where
$0\,\le \,i\,\le \,n\,-\,1,1\,\le \,j\,\le \,t\,\left( 2\,\le \,t\,\le \,\left\lfloor \frac{n}{2} \right\rfloor \right)$, the indices are taken modulo
$n$. Grigorious, Manuel, Miller, Rajan, and Stephen proved that
$\dim\left( {{C}_{n}}\left( 1,\,2,\,.\,.\,.\,,\,t \right) \right)\,\ge \,t\,+\,1$ for
$t\,<\,\left\lfloor \frac{n}{2} \right\rfloor ,\,n\,\ge \,3$, and they presented a conjecture saying that
$\dim\left( {{C}_{n}}\left( 1,\,2,\,.\,.\,.\,,\,t \right) \right)\,=\,t\,+\,p\,-\,1$ for
$n\,=\,2tk\,+\,t\,+\,p$, where
$3\,\le \,p\,\le \,t\,+\,1$. We disprove both statements. We show that if
$t\,\ge \,4$ is even, there exists an infinite set of values of
$n$ such that
$\dim\left( {{C}_{n}}\left( 1,\,2,\,.\,.\,.\,,t \right) \right)\,=\,t$. We also prove that
$\dim\left( {{C}_{n}}\left( 1,\,2,\,.\,.\,.\,,\,t \right) \right)\,\le \,t\,+\,\frac{p}{2}$ for
$n\,=\,2tk\,+\,t\,+\,p$, where
$t$ and
$p$ are even,
$t\,\ge \,4,\,2\,\le \,p\,\le \,t$, and
$k\,\ge \,1$.