Interaction of water soluble Fe(III) tetrakis(4-N-methylpyridinium)porphyrin (Fe(III)TMPyP) with sodium dodecyl sulfate (SDS) in submicellar concentrations has been studied by surface tension, optical absorption, resonance light scattering (RLS), zeta-potential, and energy dispersive X-ray spectroscopy (EDS) measurements. Measurements were conducted for a fixed concentration of Fe(III)TMPyP (6 x 10(-5) M) and SDS in various concentrations ranging between 6 x 10(-6) and 6 x 10(-2) M. Two macroscopic phase transitions, precipitation and redissolution, were observed as function of SDS concentration. The presence of a new surface active porphyrin-surfactant complex was detected. Furthermore, the presence of two oppositely charged Fe(III)TMPyP-SDS bulk moieties has been demonstrated. Possible structures for the different moieties are suggested, and the phase transitions are discussed.