ABSTRACT.Paragonimiasis is an important but neglected foodborne trematodiasis caused byParagonimus mexicanusin Costa Rica. Immunological techniques for diagnosing this parasitosis in humans do not exist in Central America. The objective of the present study was to use recombinantParagonimus westermanicysteine protease 7 to standardize an ELISA for the detection of antibodies againstParagonimusspp. Human sera positive forP. westermani,P. mexicanus, orParagonimusspp., human sera infected with other helminths, as well as sera of healthy humans without parasitic infections, were analyzed. The sensitivity of the ELISA was 92.9%, and the specificity was 91.9%. This report is the first to describe the development of an ELISA for the diagnosis ofParagonimusspp. in Costa Rica and Central America. Using this ELISA in the health system of Costa Rica is recommended to detect infections.