BACKGROUND: In the United States, the common cold has been estimated to cost more than $3.5 billion a year. Despite several randomized clinical trials, the effect of treating colds with zinc salts lozenges remains uncertain because of conflicting results. OBJECTIVE: To conduct a meta-analysis of published randomized clinical trials on the use of zinc salts lozenges in colds using a random effects model. RESULTS: Eight clinical trials of treating adults with zinc salts lozenges were identified. After excluding 2 studies that used nasal inoculation of rhinovirus, 6 trials were combined and analyzed. The summary odds ratio for the presence of any cold symptoms at 7 days was 0.50 (95% confidence interval, 0.19-1.29). CONCLUSION: Despite numerous randomized trials, the evidence for effectiveness of zinc salts lozenges in reducing the duration of common colds is still lacking.