Longitudinal spin asymmetries and $\Delta G$ at COMPASS

The spin structure $g_{1}$ of the deuteron has been measured by COMPASS with unprecedented accuracy at low $x$, providing much more reliable values for the first moment $\Gamma_{1}$ and for the quark spin contribution $\Delta\Sigma$. Difference-charge semi-inclusive asymmetries have been measured and seem to favor a flavor asymmetric polarized sea. The gluon polarization has been measured in the open-charm and high-$p_{t}$ channels. Large values of $\Delta G$ are now unlikely.