Two laboratory trials were conducted to determine the required host fish for the Carolina heelsplitter (Lasmigona decorata (Lea, 1852)), an endangered freshwater mussel (Unionidae). The first trial used glochidia from a female collected from the Yadkin-Pee Dee River basin, and the second trial used the glochidia of an adult collected from the Catawba River basin. Two different techniques were utilized for glochidia extraction: flushing and serotonin-induced release. The first female tested (Yadkin-Pee Dee) packaged most of its glochidia attached to unfertilized eggs, and extraction of glochidia by flushing the marsupia with a syringe yielded few glochidia and caused extensive tearing of the gill tissue. In the second trial (Catawba) the female was immersed in 500 mg/L serotonin creatinine sulfate, and the glochidia were readily released without injury to the adult. Several species of minnows (Cyprinidae) from both basins served as hosts. Some sunfish species (Centrarchidae) supported transformation of a few juveniles, but differences in transformation success were observed between the two basins on these species.