Ovaries from 10-day-old mice were exposed to 1.5 mol l-1 dimethylsulfoxide, 1,2-propanediol, ethanediol or glycerol for 5-60 min at room temperature before freezing. Follicles in fresh and frozen ovaries were counted and scored as normal or damaged in stained serial sections. More primordial follicles survived in ovaries frozen in dimethylsulfoxide, 1,2-propanediol and ethanediol (81-94%) than in those frozen in glycerol (4-28%). Prolonged exposure to ethanediol (60 min) before cooling decreased the survival rate, while increasing the exposure to glycerol (> or = 12 min) increased the survival rate. Fewer than 49% of primary follicles survived freezing. After transfer underneath the kidney capsules of ovariectomized immunodeficient recipients, there was no difference in the establishment of grafts of fresh (92%) and frozen (90%) ovaries, the number of recipients showing vaginal cornification (fresh, 91%, frozen 96%) or the latency of cornification (11 days). Fifteen days after transplantation, similar numbers of follicles remained in grafts of fresh ovaries, in ovaries frozen in dimethylsulfoxide and 1,2-propanediol, and in ovaries frozen after exposure to ethanediol for 5-30 min. Overall, the total number of follicles remaining in grafts of ovaries frozen in dimethylsulfoxide and 1,2-propanediol represented 42-46% of follicles present in ungrafted ovaries. This was not significantly different from grafts of fresh ovaries (63%). Dimethylsulfoxide and 1,2-propanediol are the most effective cryoprotectants for 10-day-old mouse ovaries. The majority of follicles are lost during graft establishment.