If hypertropia is observed with 6NP, multiple cranial neuropathies or a skew deviation are often considered. Understanding of the association of hypertropia with 6NP would facilitate etiologic evaluation. We retrospectively reviewed binocular alignment in a consecutive series of 43 cases of unilateral, isolated, previously unoperated 6NP. Complete 6NP was defined as inability to abduct past midline, and incomplete palsy as lesser limitation. Etiologies of 6NP included: microvascular-15, trauma-5, meningioma-4, idiopathic-3, nasopharyngeal carcinoma-2, meningitis-2, aneurysm-2, migraine-2, arteriovenous malformation-1, neovascular compression-1, retrobulbar block-1, abducens schwanomma-1, sarcoma-1, stroke-1, carotid-cavernous fistula-1, and Arnold-Chiari malformation-1. Hypertropia in any gaze position was found on objective alternate cover or Krimsky testing in 30% (13/43), and on subjective Hess screen testing in 63% (22/35) of 6NP cases. Hypertropia on objective or subjective testing were found in 50% (7/14) of patients with complete and 62% (18/29) with partial 6NP. Mean (±SD) hypertropia was 5.3Δ ± 2.2Δ, range, 2Δ -10Δ on clinical examination, and 4.7±2.1Δ, range, 2Δ -10Δ on Hess screen testing. The ipsilesional eye was hypertropic in 64% (14/22), and hypotropic in 36% (8/22) of cases. Small angle hypertropia is frequently associated with 6NP, not necessarily implying another neurological lesion. Recent anatomical and physiological studies have demonstrated that the lateral rectus muscle has separately-innervated superior and inferior compartments. Some hypertropias associated with 6NP may result from pathology weakening one lateral rectus compartment more than the other, thus inducing a vertical imbalance. Measurable hypertropia is commonly seen in unilateral, isolated 6NP, whether complete, or partial.