Tropical food crops are primarily grown in small landholder farming systems under subsistence conditions. Thus, production under low-input technology is relatively poor, and the response of different crops to improved management practices varies widely. Use of effective microorganisms (EM) in agriculture has been suggested as a way to increase crop production. The fundamental basis of the process is to develop the entire ecosystem of the field in order to utilize the inherent resource capacity, optimally and in a sustainable manner, Since this technology could produce different responses in different crops, a case study evaluated the performance of four different crops using EM technology at a single location. Emphasis was placed on the yield comparisons of each crop for the different treatments over two seasons. Treatments in the study included the use of inorganic fertilizer, EM with and without fertilizer or an organic amendment, and a control. The crops were based on farmer preference and included eggplant (Solanum melongena), vegetable beans (Phaseolus vulgaris), capsicum (Capsicum annum) and tomato (Lycopersicon esculentum). Mungbean (Vigna radiata) was cultivated during the intervening dry season. During the first wet season, the beneficial influence the EM technology was the greatest with the bean crop. The solanaceous crops did not respond to the new technology to the same extent. However, it was evident that EM enhanced the efficient use of organic matter as a source of nutrients. Yields of the control plots also increased with the use of EM. During the second wet season a greater effect of EM for increasing crop yields was evident. This confirmed earlier reports that time was required after the application of EM for the conversion of the soil ecosystem into a dymamic and zymogenic state. Introduction Vegetable production in Sri Lanka is predominantly the function of small landholders who are located in many parts of the country. This agricultural sector produces all of the domestic requirement for vegetables, and it also produces vegetables for export to nearby countries. The types of vegetables grown in different regions vary, and the selection is based on climatic and soil parameters of the specific location (Weerasinghe and Arulnandny, 1990). Vegetable production systems of Sri Lanka can be classified as either intensive, subsistence, or home garden units. The productivity of the intensive sector is dependent on heavy use of agrochemicals. In addition, in the hill county, soil and organic matter (primarily animal wastes) are brought from distant locations for use as soil conditioners. In contrast, home garden and subsistence sectors which cater to the domestic markets, especially in the drier regions, use some inorganic fertilizer. Some organic matter may be added, depending on its availability (Perera, 1989), and yields in such systems are low. The technology of effective microorganisms (EM) developed by Professor Teruo Higa at the University of the Rynkyus, Okinawa, Japan, has been identified as a potential method for increasing the utility value of most organic manures. The microorganisms, when applied in the correct manner, improve the rhizosphere by transforming the microflora and microfauna (Higa, l988). These studies suggest that the application of EM over a long period of time along with suitable organic amendments can enhance the ability of the microorganisms to increase the availability of plant nutrients in the rhizosphere. Comparative studies on the effectiveness of EM in food production is not widely reported because the technology is currently being evaluated. Thus, we examined the efficacy of EM to produce high yields of selected, commonly-grown tropical vegetables over a two-year period. The study included two types of organic matter along with the recommended inorganic fertilizer for each crop.