To determine the true usefulness of the commercially available inexpensive freezing unit (Mr Frosty) for cryopreservation of peripheral blood mononuclear cells (PBMCs), functional assays were carried out on cells that were frozen in this unit. The responses of these cells were compared with those of controlled rate frozen and fresh cells. Cell viability, recovery, proliferative responses to both phytohemagglutinin (PHA) and pokeweed mitogen (PWM), as well as interleukin (IL)-1 secreting activities of cells frozen in this container were closely comparable to controlled rate frozen cells. Although, the mean immunoglobulin (Ig) and IL-2 secreting abilities of these frozen cells were lower than the controlled rate frozen cells, these responses were still comparable to fresh cells in several of the individuals. Based on these results and considering the cost involved in controlled rate freezing method, we recommend this inexpensive unit for freezing PBMCs for subsequent immunological studies.