The main objective of this paper is to estimate the technical efficiency of cotton farms in Tajikistan using a stochastic frontier production function, and to derive the optimal farm size. Currently, Tajikistan is reforming its cotton sector. This reform consists essentially of switching from a communist system with large state owned farms to a private system. This brings the question of what the optimal size of the new private farms should be. The study involved collection and analysis of data on 205 cotton farms from the Sughd province where cotton production is concentrated. The analysis suggests that an inverse relationship between productivity and farm size does not hold. The relationship between farm size and technical efficiency is more complex than what is normally believed.