Participants with HD who have been treated with cyto-reductive chemotherapy, who are to undergo autologous stem cell transplantation, and who meet the inclusion/exclusion criteria are eligible to enter this study. The only changes to the standard of care is the addition of plerixafor to a G-CSF mobilization regimen on the day prior to apheresis and the collection of blood samples for pharmacokinetic (PK) analysis and pharmacodynamics (PD) analysis by CD34+ fluorescence-activated cell sorting (FACS) analysis. Blood samples for PK and CD34+ FACS analyses will be obtained prior to and after the first dose of plerixafor. Participants will undergo mobilization with G-CSF (10 µg/kg daily) and will receive plerixafor (240 µg/kg) on each day prior to apheresis. Participants will be apheresed for up to 5 consecutive days in order to collect the target number of CD34+ stem cells, (≥5*10^6 cells/kg). After apheresis, all participants will be treated with high dose chemotherapy in preparation for transplantation. Participants will be transplanted with cells obtained from the G-CSF plus plerixafor mobilization regimen. In the event that a sufficient number of cells for transplantation are not obtained from the collection, cells may be retained and pooled for transplantation at the investigator's discretion.