We present the results of a prospective, randomised study comparing PBPC and BM focusing on engraftment, acute and chronic GVHD and survival. Forty patients with haematological malignancies received HLA-identical sibling BM (group A) or PBPC (group B). Evaluable patients were 19 (A) and 18 (B). Median age was 35 (17–56) in A and 29.5 (9–51) in B. Conditioning was mainly Bu-Cy2; GVHD prophylaxis was CSA-MTX. PBPC were harvested after 5 days of G-CSF 10 μg/kg/day. Median days for an ANC> 0.5× 10 9/l was 18 (13–30) in A and 16 (11–25) in B (P= 0.10). Platelets> 20× 10 9/l occurred at+ 17 (10–40) in A and+ 12 (9–36) in B (P= 0.01). The probability of⩾ 2 grade a-GVHD was 19%(A) and 27%(B)(P= 0.53). The probability of all grade c-GVHD was 70% with BM. In spite of the small number of patients in group B (PBPC), our data suggest the great majority of them will have c-GVHD (P= 0.08); extensive disease was present in 50 and 100%, respectively (P= 0.05). The estimates of overall survival for A and B at 1000 days are 51 and 47%, respectively (P= 0.67); DFS at 1000 days are 52 and 58%, respectively (P= 0.50). PBPC resulted in faster platelet engraftment. The incidence of acute and chronic GVHD was similar in both groups, but the severity of c-GVHD was higher with PBPC. No differences in survival and DFS have been observed to date.