Since the introduction of hypertransfusion and intensive iron chelation therapy, patients with homozygous beta-thalassaemia major (TM) achieve adulthood. Many patients grow and develop normal hoping for marriage and to have a family. Therefore the question of fertility potential in this adult group of TM patients has become paramount. We report the semen parameters, the endocrine functions and serum zinc levels in 12 young adult TM patients. Their mean age was 24.8 years. Six patients (50%) had a normal sperm count, motility and morphology. While the remaining patients had oligospermia (sperm concentration <20 x 10(6)/ml) and/or asthenospermia (motility <40%). Basal serum gonadotrophins [LH and FSH], total and free testosterone and serum zinc did not differ significantly from those found in 13 normal adults with comparable testicular size. At the time of the study serum ferritin levels ranged from 240 to 3055 ng/ml (mean 1139 ng/ml). No correlations were found between semen parameters, serum total and free testosterone, plasma zinc, serum ferritin and seminal parameters. Nevertheless we observed that serum ferritin levels were lower (mean 543 ng/ml) in TM patients with abnormal seminal parameters (count and motility) compared to TM patients with normal seminal parameters (mean serum ferritin 1276 ng/ml; p<0.01). In conclusion, impairment of semen parameters may be a negative effect of intensive chelation therapy. Clearly, further investigations are required to evaluate if these adverse effects can be reduced or prevented, and if the existing spermatogenesis damage is reversible.