The purpose of this study was to investigate the taste properties of nucleoside analogs, which are among the current medications used to treat human immunodeficiency virus (HIV) infection. Eighteen unmedicated HIV-positive subjects and 41 healthy control subjects participated in threshold and suprathreshold experiments. All of the nucleoside medications tested were perceived as predominantly bitter (along with other qualities such as metallic, medicinal, sour, astringent, and cooling). The nucleoside analog with the lowest detection thresholds was zidovudine; the detection threshold was 1.47 mM for HIV-infected patients and 2.15 mM for control subjects. Detection thresholds for lamivudine were 4.41 mM for HIV-infected patients and 4.36 mM for control subjects. Detection thresholds for stavudine were 6.39 mM for HIV-infected patients and 5.99 mM for control subjects. Detection thresholds for didanosine were 14.29 mM for HIV-infected patients and 24.0 mM for control subjects. The nucleoside analogs also modified the taste perception of KCl and CaCl2. There were no significant differences between HIV-infected subjects and control subjects for detection threshold values for any of the drugs. However, HIV-infected subjects rated lamivudine, zidovudine, and stavudine as significantly more bitter than did the control subjects at concentrations four times higher than their detection thresholds. This result was not due to use of medications by HIV-infected subjects because none of the subjects (neither HIV-infected nor control) were taking medications.