In a previous multicenter phase III trial comparing peripheral blood stem cell transplantation (PBSCT) to bone marrow transplantation (BMT) from HLA-matched related donors, we found no statistically significant difference in the cumulative incidence of clinical extensive chronic graft-versus-host disease (GVHD) in the 2 groups. We have analyzed the results in more detail to determine whether the clinical characteristics of chronic GVHD after PBSCT might be distinct from those that occur after BMT. Clinical extensive chronic GVHD developed in 39 of 63 recipients of PBSCs and in 32 of 63 BM recipients who were alive and free of malignancy at day 100 after the transplantation. No significant differences were found in the time and type of onset of clinical extensive chronic GVHD or in the frequency of complications associated with severe morbidity. Involvement of skin and female genital tract was more frequent in PBSC recipients than in BM recipients. The cumulative incidence of chronic GVHD at 3 years was similar in the 2 groups, but the number of successive treatments needed to control chronic GVHD was higher after PBSCT than after BMT (P =.03), and the duration of glucocorticoid treatment was longer after PBSCT compared to BMT (P =.03). These results suggest that chronic GVHD after PBSCT may be more protracted and less responsive to current treatment than chronic GVHD after BMT. Assessment of the overall benefits of PBSCT compared to BMT will require continued long-term follow up of morbidity associated with chronic GVHD.