Wild potato (Solanum sect. Petota) germplasm has been collected in Mexico on nine major expeditions, as determined by 20 collections or more from each expedition currently at the United States potato genebank, the National Research Support Program-6 (NRSP-6). These have resulted in 609 accessions with good collection data. In addition, NRSP-6 has germplasm of approximately 90 other Mexican collections that are unspecific regarding date or place of collection. This expedition was funded to collect those remaining collections with no or little germplasm: Solanum clarum, S. x edinense, S. hintonii, S. hjertingii var. physaloides, S. leptosepalum, S. lesteri, S. macropilosum, S. x michoacanum, S. x sambucinum, and S. stenophyllidium. In addition, some species and species groups (species groups indicated in parentheses) have unresolved taxonomic problems that needed clarification by additional field collections. These are (S. agrimonifolium and S. oxycarpum), (S. brachycarpum, S. guerreroense, S. hougasii, and S. iopetalum - the S. brachycarpum complex), (S. fendleri, S. papita, S. stoloniferum - the S. stoloniferum complex), S. leptosepalum, and S. macropilosum. We conducted a wild potato germplasm collecting expedition in Mexico from August 22 to October 31, 1997. Our 103 collections, 71 as germplasm collections, provide the first germplasm samples for S. hjertingii var. physaloides, S. leptosepalum, and S. macropilosum. They provide additional germplasm of the rare species S. clarum, S. x edinense, S. lesteri, S. x michoacanum, S. x sambucinum, and S. stenophyllidium. We additionally gathered germplasm and field data to help resolve taxonomic difficulties in S. agrimonifolium and S. oxycarpum, the S. brachycarpum complex, and the S. stoloniferum complex.