  We study $B \to \eta' X_s$ within the framework of the Standard Model.
Several mechanisms such as $b \to \eta' s g$ from the QCD anomaly, and $b \to
\eta's $ and $B\to \eta' s \bar q$ from four-quark operators are treated
simultaneously. We find that the first mechanism give a significant
contribution to the branching ratio for $B\to \eta' X_s$, while the other two
mechanisms account for about 15% of the experimental value. The Standard Model
prediction for $B\to \eta' X_s$ is consistent with the CLEO data.
