We establish sharp concentration of mass inequality for isotropic convex bodies: there exists an absolute constant c > 0 such that if K is an isotropic convex body in \mathbbRn\mathbb{R}^{n} , then \textProb( { x ? K:||x||2 \geqslant c?nLK t } ) \leqslant exp( - ?nt ) {\text{Prob}}{\left( {{\left\{ {x \in K:||x||_{2} \geqslant c{\sqrt{n}}L_{K} t} \right\}}} \right)} \leqslant \exp {\left( { - {\sqrt{n}}t} \right)}