Total chlorine residuals of wastewater effluents as determined by an Orion 97–70 residual chlorine electrode and the phenylarsine oxide (PAO) back-titration were compared. At ≤1 ppm levels, the electrode and titrimetric methods compared favorably, but at>l ppm chlorine concentration the electrode was preferred. Use of the electrode for measuring chlorine residuals was limited to samples with a biochemical oxygen demand ≥50 mg/1 oxygen, while the PAO back-titration could be employed above this limit. The electrode was useful for field analysis; however, the electrode reading was strongly dependent upon temperature. An empirical graph was developed which allowed a post-analysis correction for the temperature differential between samples and standards.