Ho et al.1 and Baltimore and Feinberg2 (Dec. 14 issue) suggest that "residual"1 or "lingering"2 doubts about the virus-acquired immunodeficiency syndrome (AIDS) hypothesis are now resolved by new evidence of viremia in patients with AIDS.123 A paper of mine4 is cited as the source of these doubts. For the following reasons, my doubts remain unresolved.