The rheological behavior of ACT/water liquid crystalline phases containing NaCl or decane is examined here. Strong effects are noted on the elastic and loss moduli as well as on the complex and dynamic viscosities, even at low salt or decane content. Lamellar phases behave as weak gels; i.e., G' and G'' are very weak functions of frequency i n the range 10(-1)-10(2) rad/s, G' > G'', and eta* is proportional to omega-1. These effects are explained in terms of intramolelcular and colloidal forces that govern the formation of bilayers and other surfactant fluid microstructures. (C) 1994 Academic Press, Inc.