A technique has been devised for measuring the concentration of “Polyox” in dilute aqueous solutions. “Poly-ox”* is one of those polymers whose addition to water in low concentrations causes a reduction in skin friction (if the Reynolds number is sufficiently high) in turbulent flow through a pipe or boundary layer. (See, for example, ref. 1.) The analytical method is probably applicable to other polymers having this property, and it should be generally useful in this field of research. For example, in any experiment in which a polymer solution is injected at a point in a boundary layer, the method could be used to determine the distribution of polymer concentration at downstream sections. It is based on polarography, a well-established tool of chemical analysis of which an excellent account is given in ref. 2.