Stable, rod-like polyelectrolyte-surfactant aggregates (PES) are formed through association of carboxylated polystyrene and cationic surfactants. We are able to control the length and diameter of these aggregates separately through choice of surfactant and molecular weight of the polyelectrolyte. The solution behavior and structure of the aggregates at neutral pH have been fully characterized. Under these conditions the PES exhibit structural stability not seen in other oppositely charged PES systems. On lowering of the pH, the aggregates undergo a sharp structural transformation from a rodlike aggregate to one more similar to the beads-on-string structure observed in PES systems. This is explained in terms of changes in ionization of the polyelectrolyte and curvature of the surfactant interface.