Initially, techniques for autografting ovaries with or without adnexa were developed but a 30% vascular failure rate was experienced by day 14. Of the technically successful grafts, 50% proved fertile. Single vascularized ovaries with their oviducts were then allografted into bilaterally ovariectomized rabbits by microsurgical techniques and the vascular failure rate was reduced to 5% of 40 grafts. The time-course of rejection in untreated recipients was mapped by histological examination and by 24-h culture of fallopian tubes after autopsy at different times after transplantation. Control allografts were consistently rejected by day 20. Striking prolongation of both types of graft was obtained with a short 17-day course of cyclosporin A at 10 or 15 mg day-1 kg-1. Indeed, significant evidence of rejection was found in only two ovaries out of 20 so far examined histologically. Mating behaviour, ovulation, ciliary function and transport of ova appeared normal in 80% of the recipients as long as 18 weeks after stopping cyclosporin A treatment. Only one of the ovarian allografted rabbits has so far been mated and this produced seven normal young 126 days after transplantation. However, none of the five animals mated after being allografted with en bloc adnexa have so far become pregnant.