['A low-grade persisting viraemia despite long-term treatment with highly active antiretroviral therapy (HAART) has previously been demonstrated in HIV-1-infected patients. Whether ongoing viral replication also could be detected in cerebrospinal fluid (CSF) in those circumstances has not been studied before.', 'Paired CSF and blood samples from 13 neurologically asymptomatic HIV-1-infected patients on stable HAART were analysed regarding HIV-1 RNA, by using a PCR assay with a detection limit of 2 copies/ml.', 'All 13 patients had HIV-1 RNA < 2 copies/ml in CSF, compared with 8/13 in plasma.'] Do cerebrospinal fluid viral loads reach less than 2 copies/ml in HIV-1-infected patients with effective antiretroviral therapy?