Developing countries incur inordinately high economic and environmental costs to combat world-important diseases of potato. CIP has consistently endeavored to develop and improve broadly based populations for tropical and subtropical highland and lowland agroecologies, with resistances to potato late blight and viruses as primary traits. Levels of quantitative resistance to late blight and PLRV, and frequencies of extreme resistance to PVY and PVX have been increased, and progress toward early bulking has been significant in breeding pools corresponding to our agroecological targets. Alliances and strategic testing procedures with national agricultural programs are increasingly important to orient the selection of varieties that meet staple and market needs and opportunities at the local level. Given the dynamic nature of late blight, the genetic advances accomplished to date, and the desire for new varieties with market traits, increased emphasis will be given to combining key resistances, evaluation for table and processing quality, and direct links with seed production systems in targeted countries to facilitate variety development. The application of classical and molecular genetic methods that link germplasm evaluation with crop improvement will be discussed.