The common bean (Phaseolus vulgaris L.) plays a paramount role in human nutrition and
market economies throughout Eastern Africa. In this region, beans provide the second most
important source of protein after maize and the third most important source of calories after
maize and cassava (Pachico, 1993). But the predominance of local varieties1
numerous biotic and abiotic stresses contributes to significant economic losses. The response
to this situation by bean researchers has been commendable: between 1992 and 1996, 69
cultivars were released and disseminated in eight Eastern African countries (David, 1997).
While information is readily available on the performance advantages of introduced varieties,
documenting their impact at farm level presents a greater challenge.