By the time that small-scale biomass gasifiers were 'rediscovered' and promoted for use in developing countries (1970s), UNDP and the World Bank were well aware of the pitfalls of previous attempts to diffuse decentralized energy technologies. Therefore they decided to initiate a technology assessment programme before endorsing and/or stimulating a widespread gasifier introduction programme in developing countries. On July 1, 1983, the UNDP/WB worldwide "Small-scale biomass gasifier monitoring" was initiated, which was to "collect uniform data on the actual field performance, economics, safety and public acceptability of biomass gasifiers currently operating in developing countries". For the UNDP/WB program BTG developed a tar measuring protocol which was used at twenty gasifiers worldwide (Indonesia, Philippines, Brazil, Mall, Seychelles, Vanuatu and Burundi). Other parameters monitored include pressure and temperatures at various spots, gasflow, fuel consumption, lubrication oil analyses, gas-composition analyses, emission measurements. The seven year programme showed that most of donor funded projects failed, mainly because there was no sufficient commitment from involved parties. National programs on the utilization of loca available biomass resources mostly failed because the fuel did not suit the requirements of gasifier reactor. In case of proper project design/set-up most of the small scale biomass gasifiers operated without major problems. Examples of such projects are the ones in Balong and Majalengka (Indonesia) Onesua (Vanuatu), Espara Feliz (Brazil) and Dogofiry (Mali). A motivated team of technicians, operators, managers is one the most important items within this respect. Most of the heat gasifiers are installed commercially and are much more successful compared to the subsidized power gasifiers. Local manufactured gasifiers are generally constructed of low quality materials causing frequent technical problems. However, local made units are much cheaper, spares much easier accessible while repair can mostly be done on-site. Dry gas cleaning systems are recommended rather than wet cleaning systems since the concern on environmental and safety issues is generally low. The general attitude of the users is to have access to heat and/or power. In calculating the profitability of subsidized projects, mostly the owner/user don't take the depreciation costs of the installation into account since the unit was given for free. Presenting such data give afar too optimistic picture on the viability of small scale gasifiers. The financial/economic profitability of small scale gasifiers is very small and depends highly on the energy prices (biomass, diesel/fuel oil) and lack of automization.