DLAR is a receptor-like, transmembrane protein-tyrosine phosphatase in Drosophila that is expressed almost exclusively by developing neurons. Analysis of Dlar loss-of-function mutations shows that DLAR plays a key role during motoneuron growth cone guidance. Segmental nerve b (SNb) motor axons normally exit the common motor pathway, enter the ventral target region, and then synapse on specific ventral muscles. In Dlar mutant embryos, SNb axons bypass their normal target region and instead continue to extend along the common pathway. SNd motor axons also make pathfinding errors, while SNa and SNc axons appear normal. Thus, DLAR controls the ability of certain motor axons to navigate specific choices points in the developing Drosophila nervous system.