Twenty forest patches belonging to the potential domain of tropical dry forest were explored in the Cauca Valley bioregion (421,000 ha) in southwestern Colombia. Sampling was carried out from September, 2009,to October, 2010, at elevations between 930 and 1,200 m. During the field evaluations we reach 346 hours of observation distributed in 60 Km. This exploration produced the most complete list of orchids ever made in this territory, with a total of 70 species belonging to 41 genera. This figure is 112% (37 species) greater than existing records for this bioregion, and represents 1.74% of the total of orchid species reported for Colombia. Several new regional records were found, as well as at least three endemic species, probably one local extinction, and one new species for science. This figure is compared with other much smaller areas, such as the forest of Yotoco in the department of Valle del Cauca, and possible explanations for the low species richness are proposed. At the same time, a bank of digital high-resolution images of the orchid flora of the department was begun.