To the Editor.— The otherwise excellent update on human T-cell lymphotropic virus type III (HTLV-III) antibody testing 1 contains a statement that I believe needs correcting. It states that practitioners may receive referrals of antibody-positive persons for "medical counseling on a fatal and incurable disease... that has an incubation period of up to five years." Acquired immunodeficiency syndrome (AIDS) is not a disease; it is a syndrome whose criteria were strictly chosen for epidemiologic purposes. By definition, then, AIDS encompasses the fatal form of HTLV-III disease. Evidence mounts that those with irreversible disease due to HTLV-III represent only a small fraction of all those infected. The term "incubation" should not be used in regard to development of the terminal form of this viral infection; if anything, "incubation" should refer to the period between exposure and the development of biochemical or clinical objective findings. Used in this way, the incubation of