This note provides a few comments on the conditions required for similitude between velocity and electric field in electroosmotic flows. The velocity fields of certain electroosmotic flows with relatively thin electric double layers (EDLs) are known to be irrotational in regions outside of the EDL. Under restricted conditions, the velocity field, (V) over bar, can be expressed in terms of the electric field, (E) over bar, as (V) over bar = c (E) over bar, where c is a scalar constant. The irrotationality solution is certainly unique and exact for Stokes flow, but may not be stable (or unique) for flows with Reynolds numbers significantly greater than unity. (c) 2007 Elsevier Inc. All rights reserved.