The liquid crystalline phase diagrams for aqueous solutions of the homologous series of surfactants CF3(CF2)(n)CO2-Cs+ (n=5-8) have been determined. They all exhibit the classical isotropic (I)-to-discotic nematic (N-D) and N-D-to-smectic lamellar (L) sequences of transitions with increasing concentration, as previously established for the n = 6 system [N. Boden, S. A. Corne, and K. W. Jolley, J. Phys. Chem. 91, 4092 (1987)]. The effect of increasing n is to displace the transitions to higher temperatures. The behavior of all of the surfactant systems can be represented on a universal phase diagram. Both the I-to-N-D and the N-D-to-L transitions at corresponding concentrations are found to occur when the axial ratio of the disklike micelles attains a singular value in each case, irrespective of the value of n. The form of the experimental phase diagrams can be qualitatively understood in terms of a simple "zeroth" order theory which uses the results of Onsager’s theory [L. Onsager, Ann. NY Acad. Sci. 51, 627 (1949)] applied to dish to find the critical axial ratios in the coexisting isotropic and nematic phases and, separately, a dilute solution, self-assembly theory of disklike micelles [W. E. McMullen, A. Ben-Shaul, and W. M. Gelbart, J. Colloid Interface Sci. 98, 523 (1984)] to determine the temperatures at which these axial ratios are achieved at each concentration. The same treatment is also shown to account for the experimental phase behavior of mixed-chain-length systems.