Three new species in lhe caddjsfly genus Smicridea, subgenus Rhyacophylax, are described from Costa Rica and 25 additional species in the two recognized subgenera are recorded from the country. Illustrations of the male and female genitalia and wing coloration are provided for each of the new species along with a map of their distributions. Two of the new species, S. singri and S. nemorosa, are in the signota species group. and the third, S. rapanti, is a member of the peruana species group
