The pathogenesis of the Guillain-Barre syndrome (GBS) is felt to involve alterations in cellular and humoral immune responses. We report the case of a 44-year-old female with stage IV breast cancer who developed GBS 2 days after receiving high dose chemotherapy with bone marrow and peripheral progenitor cell support, and granulocyte-macrophage colony stimulating factor (GM-CSF). Her clinical status stabilized with plasmapheresis. This report lends further support to hypotheses regarding cellular immune alterations in the pathogenesis of GBS.