We have studied rose bengal (RB) in micelles carrying a positive charge (cetylpyridinium chloride (CPC) and benzalkonium chloride (BC)), a neutral charge (Triton X-100 and zwitterionic lauryl sulfobetaine (SB-12)) and a negative charge (mixture of SB-12 and sodium dodecyl sulfate (SDS)). Spectral changes during RB titration with surfactant in aqueous solution (P. Bilski, R. Debastani and C.F. Chignell, J. Phys. Chem., 95 (1991) 5784) allowed us to measure the aggregation numbers of micelles hosting RB, and to estimate the critical micelle concentrations (cmc) of the surfactants. The aggregation numbers are 37 for CPC, 41 for SB-12, 48 for Triton X-100 and 52 for mixed (6—4) SDS—SB-12 micelles, and the respective cmc are 0.22, 2.88, 0.3 and 0.5 mM. From its spectral properties in all the micelles studied, the RB molecule was found to be situated in hydrophobic micellar regions rather than adsorbed at the micellar surface. The micellar location of RB was also confirmed by quenching studies of RB fluorescence using the pyrogallol moeity, which was located outside the micelles (gallic acid), dissolved/adsorbed in the micelles (pyrogallol) or sited at the micellar interface (lauryl gallate). Lauryl gallate did not quench RB fluorescence efficiently despite the location of the pyrogallol moiety at the micellar interface. In contrast, lauryl gallate was an efficient quencher of RB fluorescence in homogenous solution. Irrespective of the micelle charge, micellar RB was more resistant to photobleaching than “free” RB and produced singlet oxygen efficiently. In cationic micelles RB was insensitive to acidic pH, which may extend the usefulness of the dye as a 1O 2 generator to acidic aqueous solutions (from pH 1.5 to 5) where “free” RB forms a colorless lactam. RB located in micelles bearing different charges may prove useful for studying 1O 2 reactions in the aqueous phase while the RB triplet state remains sequestered in the micelles.