Controlled-rate freezing of hematopoietic progenitor cells and TC-T products is the most commonly used method for cryopreservation. Due to the critical nature of the products, abnormal freeze curves are an area of concern for processing laboratories. Laboratories need to determine in which situations it is acceptable to release a product without an ideal freeze curve. This session will cover principles of cryopreservation, the effect of abnormal HPC freezing curves on potency tests and clinical outcomes and case studies of abnormal HPC freezing curves including an example of an algorithm for accepting or rejecting products.