Epidemiological studies of neuromyelitis optica (NMO) in Jamaica are lacking. Here we reviewed the clinical records of 700 patients undergoing neurological evaluation at the Kingston Public Hospital, the largest tertiary institution in Jamaica over a 4 month period. We investigated the diagnostic utility of Aquaporin-4 ImmuneglobulinG (AQP4-IgG) testing in 36 consecutive patients with a diagnosis of an inflammatory demyelinating disorder (IDD) of the central nervous system (CNS). Patients were classified into 3 categories: i) NMO, n=10; ii) multiple sclerosis (MS), n=14 and iii) unclassified IDD (n=12). All sera were tested for AQP-IgG status by cell binding assay (Euroimmun). No MS cases were positive. Ninety per cent of NMO cases were positive. Four of 12 patients with unclassified IDD tested positive for AQP4-IgG. AQP4-IgG seropositivity was associated with a lower socioeconomic status, higher EDSS (P=0.04) and lower pulmonary function than the seronegative cases (P=0.007). Aquaporin-4 autoimmunity may account for a significant proportion of Jamaican CNS IDDs.