Acute GVHD (aGVHD) is an important risk factor for predicting the incidence or severity of chronic GVHD (cGVHD). Transplant outcome can be influenced by the onset time of aGVHD in patients who have received allogeneic PBSC transplants (PBSCTs). The medical records of 134 patients who survived more than 3 months after myeloablative allogeneic PBSCT were retrospectively reviewed. In all, 38 patients (28.4%) developed grade II-IV aGVHD before day +28 (early aGVHD) and 25 patients (18.7%) after day +28 (late aGVHD). The 5-year cumulative incidence of cGVHD was 78.9% in the early-aGVHD group and 56.6% in the late-aGVHD group (P=0.034). The 5-year OS was 51.0% for the early-aGVHD and 80.8% for the late-aGVHD group (P=0.406). Infection was the primary cause of death for the early-aGVHD group (51.4 vs 16.7%, P=0.017), whereas relapse of the primary disease was higher among the patients with late aGVHD, although this was statistically insignificant (58.3 vs 25.7%, P=0.309). In a multivariate analysis, early aGVHD was identified as a risk factor for developing cGVHD (hazard ratio (HR) 2.278, P=0.004). The development of aGVHD early after allogeneic PBSCT increased the risk of cGVHD and infection-related death rate when compared with the late onset of aGVHD.