The authors present a case report of a 14-year-old boy with left ptosis and strabismus since childhood. In primary position he had left hypotropia with ptosis. On elevation of the right eye, the left eye depresses and adducts. Conversely, on depression of the right eye, the left eye elevates and abducts. This case is bidirectional, unlike the unidirectional cases of synergistic divergence described in the literature previously. This bidirectional aberrant upward movement cannot be explained by rectus muscle co-contraction. In this case, the two vertical rectus muscles show reciprocal misinnervation, or it is possible that the effect is caused by co-contraction of one of the oblique muscles.