The steadily increasing cost of nitrogen fertilizer has resulted in more emphasis on basic and applied studies to improve nitrogen use efficiency in lowland rice. The efficiency of fertilizer nitrogen in farmers' fields is shockingly low ~ a luxury resource-scarce farmers in tropical Asia can ill afford. We believe it is critical to quantify the basic transformation processes and develop management practices for higher N use efficiency for two reasons. They are: 1. Nitrogen fertilizer together with water management is a key factor for achieving the yield potentials of modern rices. 2. Fertilizer nitrogen prices are high and most Asian rice farmers are poor. The International Rice Research Institute (IRRI), Philippines; Internation- al Fertilizer Development Center (IFDC), USA; Commonwealth Scientific and Industrial Research Organization (CSIRO), Australia; U.S. Universities (Louisiana, Cornell, California, Arkansas and others); and Dr Justus Leibig University in West Germany are actively engaged in individual or collaborative research that addresses basic transformation processes on N gains and losses and management practices to maximize N use efficiency in rice. It is appropriate to update and summarize, in a double issue of Fertilizer Research, the 10 papers presented at the special symposium organized by the American Society of Agromy (ASA) at the 75th Annual Meeting in Washington, D.C. in 1983. S.K. De Datta, Head of Agromy Department, IRRI, was chairman of the International Agromy Division of ASA (A-6) in 1982 and 1983.