The paper discusses co-production in the improvement of bean varieties between Honduran hillside farmers and regional scientists. The focus is at the field level where teams of farmer-researchers (CIALs), supported by a local non-governmental organisation (NGO), the Foundation for Participatory Research with Honduran Farmers (FIPAH), collaborated in a participatory plant breeding (PPB) programme with the Pan-American Agricultural School, Zamorano. Scientists at the school crossed a popular local bean variety with improved materials, and CIAL members, trained in participatory research by FIPAH, conducted successive selections in their fields. Farmers learnt formal selection techniques, including selection from early generations, in a process that has taken more than four years to complete. Organisational analysis of the way to engage poor farmers over the long term is undertaken. Issues concerning the costs and benefits of participatory plant breeding are raised.