The formation of the polyelectrolyte- surfactant complexes has been studied. On this purpose has been measured the critical micelle concentration for every polyelectrolyte and surfactant which had been used. The phase behaviour of mixtures of a cationic polyelectrolyte (Praestol 611) and an anionic surfactant (sodium lauryl sulphate - SLS) has been studied. For a given polyelectrolyte concentration, with increasing surfactant concentration, three phase regions were identified. The first region is a single homogeneous phase. Within this region, at some surfactant concentration, above the critical aggregation concentration (cac), stable open - network 'articles' form, typically 100 nm in size, which are net positively charged. However, as the surfactant concentration is increased further, these particles aggregate and form a two - phase system: a separated gel phase, containing a high percentage of water co-existing with an aqueous surfactant phase. The rheological consequences of interactions