Motor neurons project onto specific muscles with a distinct positional bias. We have previously shown using electrophysiological techniques that overexpression of ephrin-A5 degrades this topographic map. Here, we show that positional differences in axon terminal areas, an entirely different parameter of neuromuscular topography, are also eliminated with ephrin-A5 overexpression. Therefore, we now have both morphological and electrophysiological approaches to explore the mechanisms of neuromuscular topography.