Todsen's pennyroyal (Hedeoma todsenii R. S. Irving, Lamiaceae) is a federally endangered species from the mountains of south central New Mexico that rarely produces seed. In vitro propagation methods were developed to provide material for cryostorage and for reintroduction, if that becomes necessary. Cultures were initiated from shoot tips taken from the ex situ collection at The Arboretum at Flagstaff, resulting in 12 genetic lines that were maintained on MS medium with 0.1 mg/L BAP and 0.01 mg/L NAA. Tests with other media commonly in use in CREW's Endangered Plant Propagation Program indicated that MS medium with 0.5 mg/L BAP increased shoot production and MS medium with 0.5 mg/L IBA increased root production over the maintenance medium. Other concentrations of IBA tested did not improve rooting, and a pulse of IBA followed by culture on charcoal-containing medium did not increase rooting significantly above the control. Approximately half of the plants moved to soil survived acclimatization, regardless of previous treatments. Survival through cryopreservation averaged 35% with no significant difference between the encapsulation dehydration and encapsulation vitrification procedures, and shoot tips from all 12 lines have been banked in liquid nitrogen for long-term storage. RAPD analyses indicated that there was less diversity among plants that exist in close proximity in situ than among genotypes that are separated by more distance. These propagation, cryopreservation, and genetic analysis protocols are all methods that can be used as tools to provide support for the long-term conservation of this species.