SummaryWe examined peripheral blood mononuclear leucocyte cyclic adenosine monophosphate phosphodiesterase (cAMP‐PDE) activity in 80 children (aged 2‐12 years) with atopic dermatitis. The enzyme activity (35.1 ± 18.6U) in children with atopic dermatitis was significantly higher than that (19.1 ± 12.6U) in age‐matched non‐atopic controls. There was no significant difference in the cAMP‐PDE activity between children with mild atopic dermatitis and children with severe atopic dermatitis. These findings support the view that elevation of peripheral mononuclear leucocyte cAMP‐PDE actvity in patients with atopic dermatitis is a gene‐associa