A field study was undertaken in Spring 1986 to evaluate the economic success of Guatemala's A.I.D.-supported mini-riego (MR) program to install small, self-help, auto-financed hillside sprinkler irrigation systems in highland villages. Most MR systems are pressurized by gravity and are created on a micro-scale, each serving only a few acres and families. Material costs have ranged from as little as $250 to $65,000 per system, but the majority of the 125 or so systems have been built for under $10,000 each, excluding the value of TA, general program administration and farmer-donated labor. These latter items add another 33-50% to the costs. In addition, loans for purchase of materials are granted at the concessionary rate of 2%. Despite these subsidy elements, an important feature of the program is that a significant portion of each system's total annualized social costs are auto-financed (on average, above 75%). This means, for example, that all recurring costs are the sole responsibility of the water user groups, but that these groups benefit from the cheap loans and free design and installation assistance. A survey of operations on 26 of the systems revealed that most of the MR groups have moved steadily in the direction of producing vegetable crops during the dry season, for cash markets, although the new irrigation sources are also used to augment family stockpiles of traditional foods. Analysis of the economic information obtained from 24 systems shows that all of them apparently generate positive internal rates of return (IRR's) and some of these rates are quite large. It is noteworthy that many of the systems have been inexpensive to build and maintain. Nevertheless, there has been a great diversity in installation costs and subsequent economic performance of the various systems - no two are alike. The higher-cost systems require an off-setting commitment to production of high-valued crops if the IRR is to be held up. Although there may be considerable margin of error in the reported IRR values, the data suggest that actual values for a number of these micro-sized systems are pretty impressive. A key economic success factor has been the general availability of an open market for non-traditional crop sales such as cool climate vegetables, and more exotic items such as strawberries and flowers. (Author abstract, modified).