Indomethacin membrane sensors based on different plasticizers and quaternary ammonium salt tetraoctylammonium 1-(p-chlorobenzoyl)5-methoxy-2-methyl-3-indolylacetate (INDO–TOA) were prepared. The electrode (with PVC membrane plasticized with dibutylphthalate) response to indomethacin has the sensitivity near Nernstian (-59.8±1.5 mV decade-1 ) over the linear range of 1x10-5 ÷ 1x10-2 mol L-1 and limit of detection 3.16x10-6 mol L-1. The present electrodes show clear discrimination of indomethacin ions from several inorganic, organic and some common drug excipients. This electrode has a response time 12 s and can be used in the pH range 6.0÷10.0. The notably property and attractive quality of the indomethacin sensor is low cost, comfortable application.