Recent interest in the classic fluid-mechanical problem of capillary breakup of a fluid thread has focused on similarity solutions in a variety of suggested dynamic regimes for the flow immediately before the topological singularity of pinch-off. The relationship between these will be reviewed briefly. Provided molecular dimensions are not reached first, viscous dissipation in the surrounding fluid is asymptotically dominant over inertia, and both internal and external flows are governed by the Stokes equations. Self-similar solutions for the interfacial evolution near pinch-off in this regime are obtained for different viscosity ratios l.