OBJECTIVE: Our purpose was to investigate the follicular fluid parameters associated with redox activity and the consequent production of the deleterious hydroxyl radical in β-thalassemia major. STUDY DESIGN: The levels of ferritin, total iron, total copper, and redox-active iron were measured in follicular fluid aspirated from three follicles during three consecutive ovum pickups from a patient with β-thalassemia major and were compared with the levels in nine follicles aspirates from nine healthy control patients. The redox activity in the follicular fluid samples was monitored by the extent of follicular fluid - mediated deoxyribonucleic acid degradation and salicylate hydroxylation. RESULTS: Total iron and ferritin concentrations were elevated in thalassemic follicular fluid samples compared with control samples (6.7-fold and 53.3-fold, respectively), whereas the total copper concentration was similar. Thalassemic follicular fluid samples exhibited a marked increase of redox activity, indicating a higher potential of free radical production leading to deoxyribonucleic acid degradation. Likewise, free radical - induced conversion of salicylate to dihydroxybenzoic acid derivatives was enhanced in the thalassemic follicular fluid samples compared with controls (2,3-dihydroxybenzoic acid: 67.7 ± 22 vs 20.3 ± 12.9 ng/mg protein; 2,5-dihydroxybenzoic acid: 101.6 ± 25.9 vs 4.42 ± 2.7 ng/mg protein). CONCLUSIONS: The increased level of redox activity found in the follicular fluid from a patient with β-thalassemia major focuses the attention on the small fraction of redox-active iron ions as mediators of free radical production, inducing tissue injury and possibly contributing to impairment of reproduction in these patients. (AM J OBSTET GYNECOL 1996;174:914-8.)