The shapes of the current pulses derived from fully depleted surface barrier detectors are observed and compared with theory. Separate measurements are made with low-energy alpha particles entering the front and back surfaces, so the pulses are due to the motion of electrons only, and holes only, respectively. These pulses should be of the same shape, but reversed in time and scaled in time in proportion to the mobilities. This is observed when there is a large over-voltage, but for lower voltages, straggling distorts the shape of the pulses from hole collection. The shapes of the electric fields in the detectors are surmised from the pulse shapes. At high voltage, the fields become much closer to uniform than is implied by the usual constant gradient assumption, and in two of the four detectors they become quite uniform.