Summary:Twenty-one paediatric patients (11 males and 10 females) received a CD34-selected partially matched related donor transplant for malignant (16 cases) and non-malignant conditions (five cases). The average cell dose was 11.13 ؋ 10 6 /kg. Fifteen of 16 patients with malignant conditions and one with non-malignant disease received total body irradiation plus cyclophosphamide. Three of 5 patients with non-malignant conditions and one with leukaemia, received busulphan plus cyclophosphamide. One patient with Fanconi anaemia received 100 mg/kg of cyclophosphamide. Fludarabine (25 mg/m 2 /day for 5 days) was administered prior to all these regimens. Additionally, anti-lymphocyte gamma-globulin (12.5 mg/kg/day) was administered from day ؊2 to day +2. Three (15%) patients failed to achieve complete chimaerism (CC). These patients received a second cell infusion. Two of them achieved CC. In the third patient, the percentage of donor cells was increased. The likelihood for engraftment was not related to the cell dose received. Acute graft-versus-host disease (GVHD) occurred in nine patients but only one developed GVHD Ͼgrade II. Eight patients developed active viral infections, which resolved after treatment. Patients receiving cell doses higher than our average had a significantly faster CD3 and CD4 cell recovery and experienced a lower incidence of viral infections. After 480 ؎ 255 days of median follow-up, 16/21 patients are alive and well and have CC. Three patients died of leukaemic relapse and a fourth from progression of his disease (adreno-leuko-dystrophy). We conclude that partially matched related donors are a feasible source of haemopoietic progenitor cells for transplantation for patients without matched familial or unrelated donors.