1. The aim of the present study was to assess the efficacy of pseudoephedrine in coryza. 2. In a double-blind, randomized, placebo-controlled design, 48 adults with acute coryza received a single oral dose of 60 mg pseudoephedrine (Sudafed; Pfizer Consumer HealthCare Group, Caringbah, NSW, Australia) or matching placebo. Before and after dosing, nasal airway resistance (NAR), nasal volume, the minimum intranasal cross-sectional area (MCA) and the symptom of nasal congestion were measured. 3. Pseudoephedrine produced a significant decrease in NAR (P = 0.005; 95% confidence interval (CI) 0.073, 0.383). Nasal volume increased, but this did not reach significance (P = 0.07; 95% CI -0.842, 0.034). There was no change in MCA and symptoms. 4. In conclusion, pseudoephedrine has a moderate effect in decreasing objective measures of nasal congestion in coryza.