The aim of this paper was to evaluate the efficacy of treatment with heparin in children with bronchiolitis. We studied 30 children (average age 11.3 months) with bronchiolitis; 15 subjects were submitted to a supportive therapy with an adjunct of sodium heparin (50 U/Kg/24 h i.v.) for a time lasting 24-36 hours. The control group was managed with supportive therapy only. We considered the days of the disease and the persistence of symptoms since the admission as peculiar parameters between the two groups. The results appeared to be highly significant in the heparin treated group, with a mean duration of the diseases of 3.06 days compared to 5.53 days of the controls (p less than 0.001). These data are supportive for a possible utilization of the heparin in bronchiolitis but much more experiments are needed to confirm these results.