In a double-blind clinical trial, a total of 463 volunteers were enrolled in a study designed to compare the effects of zinc gluconate lozenges (4.5 mg zinc) and a placebo for common cold. The tablets were to be taken every 1-1 1/2 waking hours at the first symptoms and for the following days until the common cold was over, but for no longer than 10 days. During the winter months of 1987 and 1988, 145 experienced a common cold and 130 completed the study. For final analysis, 61 patients in the zinc lozenge group and 69 patients in the placebo lozenge group were evaluated. Based on the patients' records the duration and severity of the common cold were compared. No statistically significant differences were found between the patient groups. Two recent studies using a five-time higher zinc dose per lozenge for common cold showed a significant, positive effect, but associated with frequent side-effects, first of all taste distortion. In the present study there was a weak tendency (not statistically significant, p = 0.12) towards more patients in the zinc lozenge group than in the placebo lozenge group reporting side-effects.