An extract of the red alga, Neorhodomela aculeata, exhibited antiviral activity against human rhinoviruses. Bioassay-guided purification was performed to yield six compounds, which were subsequently identified as lanosol (1) and five polybromocatechols (2-6) by spectroscopic methods, including 1D and 2D NMR and mass spectrometric analyses. Structurally, all of these compounds, except compound 5, contain one or two 2,3-dibromo-4,5-dihydroxyphenyl moieties. In a biological activity assay, compound 1 was found to possess antiviral activity with a 50% inhibitory concentration (IC(5)(0)) of 2.50 mug/mL against HRV2. Compound 3 showed anti-HRV2 activity, with an IC(5)(0) of 7.11 mug/mL, and anti-HRV3 activity, with an IC(5)(0) of 4.69 mug/mL, without demonstrable cytotoxicity at a concentration of 20 mug/mL. Collectively, the results suggest that compounds 1 and 3 are candidates for novel therapeutics against two different groups of human rhinovirus.