Broad band electric field data are presented which show stepped leader wave forms preceding records of distant lightning return strokes. The majority of leader pulses are characterized by a large initial peak with a small and slow opposite overshoot. Total pulse durations range from 15-40 μs several milliseconds before the return stroke to 2-10 μs immediately preceding the return stroke. Close to the ground the stepped leader pulses occur at regular 10- to 20-μs intervals and are almost unipolar with rise times of about 1 μs and full widths at half maximum in the range from 1 to 3 μs. The ratio of the peak of the last leader pulse to the subsequent return stroke peak is typically 0.1, which suggests a peak step current near the ground of about 10% of the return stroke peak current.