Sixty-eight residents of Ban Luang and Ban Pang Kae villages, in Nan Province, northern Thailand, visited our mobile field station in September 2006 and March 2007, seeking treatment for taeniasis. After treatment, 22 cases discharged tapeworm strobila in their fecal samples and 17 scolices were recovered. Among these, 3 were morphologically abnormal, with six suckers on the scolex. To confirm the species of these tapeworms, the mitochondrial cytochrome c oxidase subunit I (COI) gene was used as a molecular marker. The partial COI sequences (800 bp) of the abnormal tapeworms were identical to the sequences of Taenia saginata deposited in Genbank.