Between 1971 and 1986, 335 patients received various extracardiac valved conduits between one of the heart chambers and the pulmonary arteries. The group of patients who received aortic homograft conduits and survived the operation were analysed in detail. The age varied between 9 days and 18 years (mean 7.1 +/- 0.7 years), weight 2.4 kg-63.5 kg (mean 17.8 +/- 10.8 kg). The diameter of the conduit used was 10-30 mm (mean 20.8 mm). Multivariate analysis revealed a highly significant model (P less than 0.005) which showed that the time interval between harvesting and use of the homograft (P less than 0.02) and the earlier date of operation (P less than 0.05) were the major risk factors for obstruction. Homografts used within 3 weeks of harvesting had freedom from obstruction of 79% at 8 years; homografts used between 3-6 weeks had freedom from obstruction of only 55% at 8 years. Homografts used alone performed significantly better than those extended with woven Dacron tubes. At 10 years, 93% of homografts used alone were free of obstruction compared to 52% of homografts extended with a Dacron tube. We conclude that aortic homografts used within 3 weeks of harvesting provide a reasonably durable conduit for a period of 12 years. Longer storage, and extension of the homograft with a woven Dacron tube should be avoided.