This double-blind, placebo-controlled, one-centered, randomized clinical trial aims to assess the effects of oral calcitriol on the short-term and long-term hematologic and immunologic reconstitution after autologous peripheral blood hematopoietic stem cell transplantation. Patients age between 16 and 65 years with Hodgkin’s lymphoma, non-Hodgkin’s lymphoma, or multiple myelomas candidate for autologous peripheral blood hematopoietic stem cell transplantation will be enrolled and patients with baseline serum calcium >10.5mg/dL, phosphorous >4.5mg/dL, renal or liver complications, sensitivity to calcitriol, or disability for oral intake will be excluded. In all, 60 patients will be equally randomized between the calcitriol and placebo groups. Baseline serum levels of 25-OH-D and 1,25-(OH)2-D will be measured before the conditioning regimen. Oral calcitriol 0.25mcg or placebo pearls will be administered three times daily after the conditioning regimen up to day +30 after the transplantation. Complete blood count and differential test will be performed daily to evaluate the counts of absolute neutrophils, platelets, absolute lymphocytes, absolute monocytes, and hemoglobin. Serum level of 1,25-(OH)2-D will be also measured on days +15 and +30 after the transplantation. After a 6-month median, long-term engraftment and recovery of leukocytes, platelets, and hemoglobin as well as the disease-free survival will be assessed. Primary outcomes include the time to engraftment of absolute neutrophils, platelets, and absolute lymphocytes.