Vein patterning in the Drosophila wing provides a powerful tool to study regulation of BMP signaling. Altering levels of BMP effectors can induce major defects in the cross veins and longitudinal veins of wings. The extracellular protease AdamTS-B (CG4096) encodes an ADAMTS protease expressed in the embryonic trachea and wing imaginal disc precursor cells. The absence of AdamTS-B displayed an extra PCV vein, and a branched or incomplete distal tip of the longitudinal L5 vein. These defects were similar to over-expression of BMP agonist crossveinless (cv), and down-regulation of the BMP inhibitor short gastrulation (sog). The defects observed in over-expression of AdamTS-B were also similar to those of sog up-regulation and cv knock-down mutations; PCV were not formed completely. Furthermore, the downstream effector of BMP signaling, pMad, showed altered expression levels consistent with the PCV defects seen in the loss and over-expression of AdamTS-B. These findings suggest that AdamTS-B might be a BMP antagonist, modifying BMP agonists or receptors to alter BMP signals. Further study needs to be undertaken to fully unravel interactions between AdamTS-B and BMP signaling.