This article reviews and critiques the frontier literature dealing with farm level efficiency in developing countries. A total of 30 studies from 14 different countries are examined. The country that has received most attention is India, while rice has been the most studied agricultural product. The average technical efficiency (TE) index from all the studies reviewed is 72%. The few studies reporting allocative and economic efficiency show an average of 68% and 43%, respectively. These results suggest that there is considerable room to increase agricultural output without additional inputs and given existing technology. Several of the studies reviewed have sought to explain farm level variation in TE. The variables most frequently used for this purpose have been farmer education and experience, contacts with extension, access to credit, and farm size. With the exception of farm size, the results reveal that these variables tend to have a positive and statistically significant impact on TE. This paper shows that considerable effort has been devoted to measuring efficiency in developing country agriculture using a wide range of frontier models. Despite all this work, the extent to which efficiency measures are sensitive to the choice of methodology remains uncertain.