The fluorescence quenching of o-aminobenzoic acid by ethylene trithiocarbonate in cetyltrimethylammonium bromide (CTAB) and p- tert-octylphenoxy-polyoxyethylene ether (TX100) was studied using steady state and time-resolved fluorescence techniques. The critical micelle concentrations of CTAB and TX100 can be estimated from the Stern—Volmer quenching parameters. Such parameters, including the fluorescence lifetime and quantum yields in CTAB, are presented. The anionic surfactant sodium dodecylsulphate (SDS) has little affect on the quenching process.