The effects of additives in aqueous threadlike micellar systems formed with cetyltrimethylammonium bromide (CTAB) were studied by means of dynamic viscoelastic and ¹H-NMR techniques. An additive used was an ionic aromatic compound, sodium p-toluenesulfonate (NapTS). Viscoelastic behaviors of an aqueous CTAB and NapTS system essentially agreed with those of an aqueous system sodium salicylate (NaSal). When a ratio of NapTS concentration (C_S) to CTAB concentration (C_D) was higher than unity, the CTAB:NapTS/W system possessed the single relaxation viscoelasticity. The longest relaxation times (τ_m) depended on the concentration (C_S^*) of NapTS in the bulk aqueous phase, whereas τ_m was independent of C_D.