AbstractA systems analytic approach, in which one tries systematically to examine a variety of considerations together rather than in parts, is essential whenever neglect of the interactions of the parts of the system might lead to erroneous conclusions. The O.R. attitude is even more important for developing countries, where the problems are many and solutions are much more severely constrained than in developed countries owing to resource limitation, scarcity of skills, inadequate technological and managerial infrastructure to support sophisticated solutions, and the variety of traditional and‘modern’attitudes prevailing in developing societies. To illustrate this, a number of applications carried out by the author in India, covering efficient resource allocation for economic planning, optimal use of resources, such as water and fertilizer, and the choice of techniques of power systems, as well as organizational problems of identification and introduction of appropriate technology in building construction and community bio-gas plants, are briefly described along with comments on the implementation of the results.