Seed of 36 dooryard and wild accessions of Gossypium hirsutum and one G. barbadense were collected in the Yucatan Peninsula of Mexico and seed of one atypical G. hirsutum and one G. cf. aridum (a diploid species) were collected near the southern (Pacific) side of the Isthmus of Tehuantepec. The 39 accessions collected will add to the cotton germplasm diversity. In addition, 25 other sites where Gossypium was growing but had no mature seed were recorded for future expeditions. The cotton collecting expedition was a collaborative project between ARS, USDA and SARH, INIA (Secretaria de Agricultura y Recursos Hidraulicos, Instituto Nacional de Investigaciones Agricolas), Mexico. We represented ARS, USDA, and Dr. Arturo Hernandez and Ing. Fernando de Leon represented SARH, INIA.