A survey of the density field in the immediate vicinity of Jarvis Island was made in April 1971. The island is isolated and is situated in the Pacific Equatorial Undercurrent, thus presenting the opportunity to study a high Reynolds number (∼ 109) stratified shear flow. Large deflexions of the isopycnals were observed near the island. Solutions derived from the perfect-fluid equations of Drazin (1961) axe in reasonable agreement with the observed mass field in the upstream region. Downstream, a wake region was apparent, but the dynamics of the wake are obscure. A coefficient of pressure deficit in the wake is in the same range as values computed from homogeneous laboratory flows, but baroclinic effects are observed.