All three patients complained of cough, fever and dyspnea. Their chest X-ray films revealed interstitial changes such as Kerley B lines. The results of lymphocyte stimulation tests were all negative for Minocycline (MINO), whereas the provocation tests were all positive in three cases. The onsets of symptoms appeared 7, 12 and 9 hours after administration of MINO respectively, which suggested type III allergy in terms of the latency period. In cases No. 1 and No. 3, lung tissue specimens obtained by transbronchial biopsy showed findings of mild acute eosinophilic pneumonia. The bronchoalveolar lavage fluid of case No. 3 showed eosinophilia. On diagnosing MINO-induced pneumonitis, the lymphocyte stimulation test is not always beneficial, whereas the provocation test is supposed to be a safe and sure method.