Our objective was to assess the feasibility of F-18-FDG PET/CT for noninvasive monitoring of treatment response after allogeneic stem cell transplantation (SCT) for myelofibrosis. Methods: Twelve patients with myelofibrosis underwent F-18-FDG PET/CT before and after SCT. Bone marrow uptake, spleen uptake, and spleen size were assessed before and after SCT and compared with hematologic response criteria and bone marrow biopsies. Results: All patients who did not achieve complete remission remained PET-positive (P = 0.02). Extent of disease, bone marrow metabolism, spleen metabolism, and spleen volume decreased significantly in patients with complete remission (P = 0.03). PET/CT after SCT had a sensitivity of 1.0 (95% confidence interval [CI], 0.54-1.0), a specificity of 0.83 (95% CI, 0.36-1.0), a negative predictive value of 1.0 (95% CI, 0.48-1.0), and a positive predictive value of 0.86 (95% CI, 0.42-1.0) for diagnosis of residual disease. Conclusion: F-18-FDG PET/CT is feasible for noninvasive monitoring of treatment response after allogeneic SCT for myelofibrosis.