Physical characteristics such as sand grain size and humidity were determined and the relation between the examined parameters and nesting success, nest density, and hatchling success of green turtles on Samandag Beach, Hatay, Turkey were investigated in this study. Coarse sand and low humidity at the river site and fine sand and high humidity at distances perpendicular to the river mouth were determined. The wind speed and direction toward land on the beach are important factors forming grain structure on Samandag Beach. The mean particle size, about 350 mu m, at nesting locations (N) of green turtles is smaller than that at nonnesting areas (NT and T). Nesting sites have the lowest uniformity coefficients (C-u = 2.78) on the surface than in no-nest no-track sites (C-u = 3.48) and in only-track sites (C-u = 3.5) on the surface. A negative correlation exists between sand moisture and nesting success with respect to increasing distance from Cevlik Harbor for Chelonia mydas. The hatchling success of C. mydas was found to be significantly affected by sand moisture. When sand moisture is above 8%, hatchling success become too low or no successful hatching occurs.