This protocol describes how to harden or acclimatize tissue culture-derived yam (Dioscorea) plantlets before transplanting them in the soil. Briefly, the plantlets are first put in pots with a vermiculite and peat moss mixture, and the pots are placed in a humidity chamber, where they are sprayed and watered daily. After 2 wk, the plants are transplanted to pots or plastic bags with ordinary or sterile soil and watered daily. After another 2 wk, they are transplanted into the field.