The laser-induced breakdown power (P^B) was measured for various neat liquids and various combinations of miscible liquids. P^B for the neat liquids and the mixtures was found to be proportional to 1/n² (n² is the nonlinear index of refraction). From this result, we conclude that self-focusing dominates the breakdown process for these liquids (CS², benzene, nitrobenzene, chlorobenzene, bromobenzene, and toulene). The dependence of P^B for the neat liquids and mixtures on the f-number of the focusing optics was then measured and found to be in excellent agreement with the predictions of self-focusing theory for liquids with large n²'s. The liquids were then used as a “model system” to compare the results of similar measurements in single-crystal NaCl. This comparison indicates that the observed focal spot-size dependence in NaCl is not due to self-focusing.