Given a positive integer $n$, a finite field ${{\mathbb{F}}_{q}}$ of $q$ elements ($q$ odd), and a non-degenerate symmetric bilinear form $B$ on $\mathbb{F}_{q}^{n}$, we determine the largest possible cardinality of pairwise $B$-orthogonal subsets $\varepsilon \,\subseteq \,\mathbb{F}_{q}^{n}$, that is, for any two vectors $x,\,y\,\in \,\varepsilon $, one has $B(x,\,y)\,=\,0$.