The skin from fresh human cadavers and guinea pigs was stored in 4 degrees C, -20 degrees C, -80 degrees C and -196 degrees C deep freezing for six different periods (1, 2, 3, 5, 7 and 14 days). The number and morphology of Langerhans cells (LC) were observed using Juhlin's ATP-ase dye method. It was found that the epidermal LC of cryopreserved skin decreased significantly in number, and there was a marked change in shape, as compared with fresh skin grout (P < 0.01), except for those in 4 degrees C groups (for 1, 2, 3 days). The mean value of LC in -196 degrees C group, which was 40%-50% of that of fresh skin, was the lowest among all the groups. The number of LC dropped most rapidly in the -196 degrees C group after one day freezing. The changes in LC in the stored skin may play an important role in prolongation of rejection time after transplantation.