The wind turbine technology has a unique technical identity and unique demands in terms of the methods used for design. Remarkable advances in wind power design have been achieved due to modem technological developments. Since 1980, advances in aerodynamics, structural dynamics, and "micrometeorology" have contributed to a five percent annual increase in the energy yield of the turbines. Current research techniques are producing stronger, lighter, and more efficient blades for the turbines. The annual energy output per turbine has increased enormously and the weight of turbine and the noise they emit have been halved over the last few years. The deployment of modem wind turbines has resulted in experience in the production and use of wind turbines, which has led to improved turbines and reduced cost of wind-generated electricity. The paper reviews the research and development of technology of wind turbines and its impact on the cost of wind energy systems. Also the important gaps between the theoretical research and practical implementation have been analyzed and the problems associated with this have been discussed. The need and areas for further research and development effort have also been outlined.