To the Editor: Hersh et al. recently described high levels of circulating thymosin α₁ in homosexual men being evaluated for possible AIDS.¹ The authors then speculated that the high levels might have resulted from an attempt by the thymus to stimulate production of helper cells in persons with low levels — an end-organ–failure hypothesis. If this was so, the thymosin α₁ levels should have correlated inversely with helper-cell levels or helpensuppressor ratios. We have examined thymosin α₁ levels in 73 Danish homosexual men. Although they were generally healthy volunteers and none had symptoms or signs of AIDS,.