Data concerning the experimental induction in guinea-pigs of hypersensitivity pneumonitis with a cockroach antigen are presented. A glycoprotein obtained from the chitinous structures of Periplaneta americana was aerosolized daily to guinea-pigs during 12 weeks. The presence of specific antibodies (IgG) was detected by serological techniques; histopathological studies of the lungs showed interstitial infiltrates of macrophages and LT-CD8+ cells, as revealed by the MoAb used. Single non-necrotizing granulomas were characteristic from the 10th week to the end of the experiment. The results from this animal model suggest that this hypersensitivity pneumonitis is a typical delayed-type reaction due to chronic contact with the heterologous glycoproteins of P. americana.