The strengths and weaknesses of the evolving techniques used by researchers in Bolivia to evaluate potato germplasm with farmers are assessed. When detailed knowledge of farmers' criteria is required, questionnaires or forms are most appropriate; otherwise techniques from participatory rural appraisal could be used. Initially, when evaluating large numbers of clones, scientists' and farmers' choices tended to coincide, although subsequently they diverged. This suggested that it may be more efficient to involve farmers later in the selection process, ensuring that an interesting amount of diversity still exists, and work to improve breeders' knowledge of farmers' criteria. Integration between social scientists and breeders was less than ideal at the start of the study, reducing the impact of farmer evaluations on the breeding programme.