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Let $C\subset \mathbb P^r$ be an integral projective curve. We define thespeciality index $e(C)$ of $C$ as the maximal integer $t$ such that$h^0(C,\omega_C(-t))>0$, where $\omega_C$ denotes the dualizing sheaf of $C$.In the present paper we consider $C\subset \mathbb P^5$ an integral degree $d$curve and we denote by $s$ the minimal degree for which there exists ahypersurface of degree $s$ containing $C$. We assume that $C$ is contained intwo smooth hypersurfaces $F$ and $G$, with $deg(F)=n>k=deg (G)$. We assumeadditionally that $F$ is Noether-Lefschetz general, i.e. that the $2$-thN\'eron-Severi group of $F$ is generated by the linear section class. Our mainresult is that in this case the speciality index is bounded as $e(C)\leq{\frac{d}{snk}}+s+n+k-6.$ Moreover equality holds if and only if $C$ is acomplete intersection of $T:=F\cap G$ with hypersurfaces of degrees $s$ and${\frac{d}{snk}}$.

A speciality Theorem for curves in $\mathbb{P}^5$ contained in Noether-Lefschetz general fourfolds