Abstract: The fluorescence spectra of N-alkylindoles and 3-methyl-N-alkylindoles with various chain lengths in dimethyl sulfoxide-water(DMSO-H_2O) were studied under stationary and nonstationary condition. As the fraction of water in solvent mixture (Φ) increases, the indoles with short chain display red shifts in fluorescence λ_(max) and increases in fluorescence lifetime. On the contrary, the fluorescence λ_(max) of long chain indoles shift to blue side and their fluorescence lifetimes decrease with increasing in Φ. This observation supports intermolecular aggregation of long chain indoles in poor solvents, The microscopic polarity in aggregates is similar to that in cyclohexane. The distribution of indoles between bulk solution and aggregates was determined by time resolved fluorescence technique.