A cryopreservation procedure was developed for gametophytes of Laminaria digitata using an encapsulation-dehydration technique. Cells were encapsulated in calcium alginate beads pretreated for 6 h in liquid medium containing 0.3 to 0.5 M sucrose and then dehydrated. Freezing was performed in two steps, the first consisting of a slow temperature decrease from 19°C to -40°C and the second of direct immersion of samples in liquid nitrogen. Thawing was performed in a water bath at 40°C for 2 min. Survival rates were between 25 and 75% depending on age, sex and stress. The best results were obtained with alginate beads pretreated for 6 h in a 0.3-0.4 M sucrose solution and dehydrated down to 40% of the initial wet weight. Recovery time was about two weeks.