ObjectiveTo review the efficacy of the ribosomal immunostimulant Ribomunyl®in preventing upper and lower respiratory tract infections.Design and settingReview of studies of 3 and 6 months’ duration comprising part of the international registration file.PatientsData from 2117 patients (1215 children and 902 adults); ribosomal immunostimulant n = 1062, placebo n = 1055.ResultsNineteen randomised, double-blind, placebo-controlled clinical trials were performed between 1983 and 1994 in Europe. In children with ear-nose-throat (ENT) infections, 3 months’ ribosomal immunostimulant treatment significantly decreased the mean number of recurrences (27–68% reduction), and reduced the duration of infection (28–66% reduction) and antibacterial requirement (29–60% reduction). Ribosomal immunostimulant was similarly effective in children with ENT and bronchopulmonary infections, reducing the mean number of recurrences by 32–61% compared with placebo. In children with otitis media, ribosomal immunostimulant reduced recurrences by 10–53% and also reduced the duration of infection, antibacterial use and local surgery requirement. Results obtained from studies of 6 months’ duration confirmed or extended these results. In adult patients with ENT or mixed respiratory infections, ribosomal immunostimulant produced similar reductions to those seen in children for recurrent infections (54–78% reduction), duration of infection (42–79% reduction) and antibacterial use (38% reduction).ConclusionsThese results clearly demonstrate that ribosomal immunostimulant is effective in preventing and in reducing upper and lower respiratory tract infections in children and adults.