The purpose of the article is to assess technical, pure technical, and scale efficiency of the production of grain and leguminous crops in Ukraine and identify sources of inefficiency by the DEA method. Research methods. In the research process were used the following scientific methods: the econometric method (for checking the quality of input and output parameters of the research objects); the DEA method (for assessing technical, pure technical, and scale efficiency of the studied agricultural enterprises and identifying sources of inefficiency). Research results. According to the calculations, in 2018, enterprises of Kirovograd, Odesa, Sumy, Cherkasy, and Chernihiv regions worked at the maximum possible levels of productivity. The average technical efficiency was 0.794. This means that almost 20 percent of the amount of calculated inputs can be decreased without reducing the amount of output. It was revealed that, in 2018, the non-optimal scale was the main source of technical inefficiency of agricultural enterprises of Vinnytsia, Volyn, Donetsk, Zhytomyr, Luhansk, Lviv, Mykolaiv, Poltava, Ternopil, and Kherson regions. The main source of technical inefficiency of agricultural enterprises in Dnipropetrovsk, Zaporizhzhia, Kyiv, Kharkiv, and Khmelnytskyi regions was the ineffective work of managers in production process management. Partially technical inefficiency of enterprises in these regions was the result of non-optimal scale. Elements of scientific novelty. Features for the application of the DEA method to assessment of technical, pure technical, and scale efficiency of agricultural enterprises and identification of reasons of inefficient work were identified. Practical significance. The research results can be used to rank agricultural enterprises by their effectiveness, and eliminate the identified reasons of inefficient work. Tabl.: 3. Figs.: 1. Refs.: 10