Thirteen new gravity profiles, 16,000 km in total extent, cover all the major tectonic regions of Melanesia. The isostatic balance of individual features is judged from comparison of free air to Bouguer anomalies. Isostatic anomalies are also shown for two representative profiles. Topography is the key factor producing free air anomalies over the trenches and adjacent ridges despite variations in tectonics. The Manus, South Mussau, and Vityaz trenches along the northern border of Melanesia are less deep than the Tonga and New Hebrides trenches and accordingly show smaller amplitude free air anomaly minima. Long-wavelength free air highs south of the New Hebrides Trench, over Solomon Sea, and probably west of North Mussau Trench, support the idea of lithospheric uparching suggested by A. B. Watts, and M. Talwani. A large amount of our data delineates predominantly positive free air anomalies over the Bismarck and Fiji plateaus, the result being consistent with earlier measurements. A representative profile across the Lord Howe Rise indicates a significant correlation of free air and isostatic anomalies with topography. Gravity anomalies over some local topographic features are discussed.