We present thresholds for optical breakdown in bulk transparent solids and water with 100-fs laser pulses. In solids, we used microscopy and scattering techniques to determine thresholds for plasma formation and permanent damage in a wide variety of materials. Transmission measurements show that damage occurs at energies where there is little absorption of the laser pulse. In water, we used scattering and acoustic techniques to measure the breakdown threshold for 100-fs pulses. In contrast to solids, transmission measurements in water indicate that there is no plasma or bubble formation unless there is significant absorption. For comparison, we also measured breakdown thresholds for 200- ps pulses.