We have investigated the uniaxial elongation behavior of six different wormlike micelle systems covering a broad range of surfactant concentrations c(s) and salt/surfactant ratios R using the capillary breakup elongational rheometry (CaBER). In the fast-breaking limit (high c(s) and R), filament lifetime t(fil) is controlled by the equilibrium shear modulus G(0) and the breakage time lambda(br) obtained from small oscillatory shear according to t(fil)/G(0) proportional to lambda(2/3)(br) and relaxation time ratios lambda(e)/lambda(s) approximate to 1 are found. When reptation dominates (high c(s), low R) lambda(e)/lambda(s) < 1 is observed similar as for solutions of covalently bound polymers. In this concentration regime, the micellar structure seems not to be affected by the strong elongational flow. In contrast, high filament lifetimes up to 1000 s and lambda(e)/lambda(s) values up to 10 are observed at low c(s) irrespective of R. This indicates the formation of elongation-induced structures (EISs). A minimum viscosity and a minimum initial diameter are required for creating EIS. Additional filament stretching experiments indicate that a critical total deformation has to be exceeded for structure build-up. Finally, our experiments reveal a distinct difference regarding the dependence between solutions of linear and branched micelles of filament lifetime on viscosity suggesting that CaBER is a versatile means to distinguish between these structures. (C) 2014 The Society of Rheology.