AbstractFour different polymer‐modified mercury film electrodes (MFEs) on a glassy carbon substrate were tested for their ability to determine lead and cadmium in the presence of surfactants. The polymers used for electrode modification were: Nafion, polyaniline, base‐hydrolyzed cellulose acetate, and base‐hydrolyzed poly(ethyl 3‐thiophene acetate). Triton X‐100, sodium dodecyl sulfate, dodecyl pyridinium chloride, and bovine serum albumin were chosen as representatives of surface active compounds. It is shown that polymer‐covered electrodes are useful in surfactant‐containing media in some instances, but none of them remained unaffected by any of the four surfactants. The cellulose acetate electrodes seem to be less affected by proteins than the bare MFE and other modified electrodes. The Nafion and cellulose acetate‐coated electrodes were used for the determination of lead in filtered and acidified, but otherwise untreated, water samples from a sewage treatment plant. The results obtained with the cellulose acetate‐coated electrode were in good agreement with those from atomic absorp