Monopiles are often used foundation concepts for offshore wind turbine converters. These piles are highly subjected to latereal loads and overturning moments due to wind and wave forces. Typically, monopiles with diameters of 4 to 6 m and embedded pile lenghts of 15 to 30 m are necessart. In current practice, these piles are normally designed by the p-y curve method although the method is developed and verified for small-diameter, slender piles with diameters up to approximately 2 m. In the present paper, a review of the existing p-y curve formulations for piles in sand is presented. Based on numerical and experimental studies presented in the literature, advances and limitations of the current p-y curve formulations are outlined.