Measurements of conductivity in aqueous solution are recommended for studying the behavior of some dyes. The conductivity of two azo dyes C.I. Acid Red 151 (AR 151) and C.I. Mordant green 17 (MG17) have been studied. The ionization degree, α and Van,t Hoff's factor ,i, were calculated; their values decrease with increasing dye concentration and increase with increasing temperature. The mobility, µ, the activation energy, E, were also calculated. The findings indicate that interionic attractions and connections are present. Dyes ions tend to self-associate. Since these textile dyes were applied from aqueous systems, it is important to understand the association of dyes. The molecular aggregation of two sulphonated dyes studied by measuring the electrolytic conductivity in aqueous solutions as a function of dye concentration and temperature. Aggregation number, aggregation constant and shape of aggregate were calculated. As expected the aggregation number decreases with increasing temperature, and that tends to J-aggregation which enhance the devices performance such as xerography, sensors in presence of different additives.