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 mu g/kg/day, Median days for an ANC >0.5 x 10(9)/l was 18 (13-30) in A and 16 (11-25) in B (P = 0.10), Platelets >20 x 10(9)/l occurred at +17 (10-40) in A and +12 (9-36) in B (P = 0.01), The probability of greater than or equal to 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.