The fundamental characteristics of the "photosurfactant" 4-ethylazobenzene 4’-(oxyethyl)trimethylammonium bromide (EZTABr) have been studied in comparison with those of dodecyltximethylammonium bromide (DTABr), a typical cationic surfactant. The photosurfactant undergoes a trans/cis transition on UV/vis irradiation. The relative contents of the trans and cis forms are analyzed by HPLC. Combined with the trans/cis composition, the trans and cis electronic spectra are obtained. The electrical conductivity experiment revealed that UV irradiation increases the critical micelle concentration (cmc) as a function of the cis-form content. The cmc of the pure cis form is evaluated based on an ideal mixed micelle model. The surface tension experiment indicated that the cis form is significantly less surface active than the trans form, and the surface adsorption of the trans form is a little weaker than that of DTABr.