Let S be a set of n points in
${\mathbb R}^{2}$ contained in an algebraic curve C of degree d. We prove that the number of distinct distances determined by S is at least cdn 4/3, unless C contains a line or a circle.
We also prove the lower bound cd ′ min{m 2/3 n 2/3, m 2, n 2} for the number of distinct distances between m points on one irreducible plane algebraic curve and n points on another, unless the two curves are parallel lines, orthogonal lines, or concentric circles. This generalizes a result on distances between lines of Sharir, Sheffer and Solymosi in [19].