Exposure of WI-38 cells to ascorbic acid plus glutathione mixtures in growth medium for 2 days prior to infection with rhinovirus serotype 20 and during virus replication suppressed multicyclic but not single-cycle growth of the virus. Multi-cyclic growth was suppressed over the range of multiplicity of infection (m.o.i.) of 4 × 10−1-4 × 10−4 PFU/cell. There was some suggestion that, in the presence of ascorbic acid plus glutathione, interferon was produced at the highest m.o.i. tested but at barely detectable levels.