Based on collecting trace aniline on a membrane filter and dissolving the filter in an organic solvent, a simple and rapid preconcentration technique has been proposed for its spectrophotometric determination in water samples. In 0.1M of hydrochloric acid medium, aniline diazotizes with nitrous acid, which is then coupled with N-(1-naphthyl)-ethylenediamine at the same acidity. The azo-dye formed is collected on a 0.45μm nitrocellulose filter at pH 5.0 of acetate buffer solution in the presence of surfactant tetradecylpyridinium chloride. The dye with the filter is dissolved in a small volume of 2-methoxyethanol acidified with hydrochloric acid, and the absorbance of the resulting solution is measured at 560 nm against a reagent blank. Detection limits better than 1.0μg · L−1of C6H5NH2can be achieved. The components normally present in water do not interfere when a masking agent solution is added. The proposed method has been applied to the analysis of water samples from several sources. The recoveries of the aniline added to the samples are quantitative, and results found are satisfactory.