Patients with hematological malignancies (HMs) and that undergoing hematopoietic stem cell transplantation (HSCT) for HMs or other disorders require multiple blood product transfusions. Approximately 30% of these patients develop platelet transfusion refractoriness (PTR), which increases the risk of serious and potentially fatal bleeding complications. The incidence of PTR in the Saudi population is unknown.To determine the occurrence of PTR in adult HMs and HSCT patients at King Abdul-Aziz Medical City (KAMC), Riyadh, we performed a study of 29 HMs and HSCT patients. Platelet counts were determined prior to and one hour after each platelet transfusion event. Four (13.8%) patients qualified for PTR, as they had corrected count increment of less than 5000 following two consecutive platelet transfusions. PTR was detected following 17 of the 102 (16.7%) platelet transfusion events. Subgroup analysis showed a significant association between the patient's diagnosis and the development of PTR (75.0% CML, 18.9% NHL, 16.7% AML, 7.1% ALL, 0.0% HL p=0.011). No significant correlations between the development of PTR and either age, history of HSCT or previous exposure to blood products were found. Our observed incidence of PTR in Saudi HM and HSCT patients is significantly lower than the reported worldwide incidence (24-34%), which might be attributable to consanguinity within the community. Patients with AML and NHL might be at a higher risk of developing PTR.