The S 35 variety is a nonphotoperid-sensitive, high-yielding, early-maturing, and drought-tolerant pure line that originated from ICRISAT's breeding program in India, and was later advanced and promoted in Cameroon and Chad. Its introduction into drought-prone areas of Chad has been very successful with a net present value of research investments estimated at US$ 15 million, representing an internal rate of return of 95%. Two crucial factors explain this apparent success: (1) germplasm research spillovers from ICRISAT and Cameroon's breeding programs substantially reduced the time lag in S 35 research and development in Chad; and (2) the FAO/UNDP-supported seed project at Gassi not only successfully multiplied S 35 seed on a large scale, but also distributed it to farmers by adopting the mini-doses approach and involving the Office national de developpement rural and NGOs. Since the recommended management practices of S 35 adoption are simple, relatively easy to implement with available family labor and animal traction, and are not capital intensive, the technology has found favor with many farmers. Between 1990 and 1995, the percentage of adopting farmers grew from 14% to 80%. In 1990, 7% of the total sorghum area (13 000 ha) was sown to the S 35 variety. By 1995, the area under S 35 had increased to 27% (66 000 ha). A yield advantage of about 51% over farmers' local varieties is associated with the adoption of S 35. Three major constraints cited by farmers - susceptibility of the variety to bird attack, the high cost of seed, and low soil fertility - should assist in the formulation of future research priorities.