GVHD has a major role in the morbidity after a BMT, even if the donors are HLA matched siblings. The risks of a severe GVHD increase when using partially matched family donors or matched unrelated donors. An acute GVHD occurs within 100 days from BMT, whereas a chronic GVHD occurs in the first year. Both acute and chronic GVHD are less frequent and severe in children. The experience of the transplant team of Pavia is in agreement with this statement. The incidence of GVHD was extremely low even then compared with the data of the Italian pediatric BMT group. In transplant performed with HLA matched donors the incidences of severe acute and chronic GVHD were 5 and 8%.