Lipoxin A4 (LXA₄) is a biologically active eicosanoid produced in human airways which displays anti-inflammatory properties. In cystic fibrosis (CF) and severe asthma, LXA₄ production has been reported to be decreased and in such diseases, one of the consequences of airway inflammation is disruption of the tight junctions (TJ). In the present study, we investigated the possible role of LXA₄ on tight junction formation, using transepithelial electrical resistance (TER) measurements, Western blotting and immunofluorescence. We observed that exposure to LXA₄ (100 nM) for 2 days significantly increased ZO-1, claudin-1 and occludin expression at the plasma-membrane of confluent human bronchial epithelial 16HBE14o- cells. LXA₄ (100 nM) stimulated the daily increase of the 16HBE14o- cell monolayers TER and this effect was inhibited by boc-2 (LXA₄ receptor antagonist). LXA₄ also had a rapid effect on ZO-1 immunofluorescence at the plasma-membrane and increased TER within 10 min. In conclusion, our experiments provide evidence that LXA₄ plays certainly a new role for the regulation of tight junction formation and stimulation of the localization and expression of ZO-1 at the plasma membrane through a mechanism involving the receptor ALX.