The nasal absorption of zidovudine (AZT) and its subsequent transport to cerebrospinal fluid (CSF) was examined in rats. Both rapid absorption and a high CSF concentration were observed after the nasal application. Plasma and CSF concentrations of AZT increased when probenecid was coadministered with AZT. Thus, this nasal coadministration of AZT and probenecid could be useful for the treatment of AIDS patients with neuropathies.