In the current study the AML is already in remission after intensive chemotherapy. In an attempt to design a conditioning strategy with very low toxicity but considerable myelosuppressive activity, the investigators will combine the non-myeloablative (NMA) fludarabine and low-dose TBI (2 Gray) with a 10-day schedule of decitabine (Dec-Flu-TBI). Theoretically, it is very attractive to add a drug like decitabine (in a 10-day schedule) that exerts a strong antileukemic effect, without additional extra-medullary toxicity, to the standard Flu-TBI NMA conditioning regimen. The hypothesis is that in this way the investigators can extent the time the immune system of the donor needs to create an adequate graft-versus-leukemia effect, at the cost of low toxicity.