Studies on the implication of mycobacteria in the pathogenesis of sarcoidosis have generated conflicting results. In an attempt to further elucidate the etiology of the disease, we obtained broncho-alveolar lavage (BAL) samples from sarcoidal patients, which were subsequently used for intra-tracheal inoculation of a group of rabbits. Patients were characterized as sarcoidal on the grounds of clinical, radiographic, histological and microbiological testing. Four months following inoculation, lung and alveolar lymph node specimens were collected from the animals and were examined by means of histology and microbiology, as well as by a polymerase chain reaction (PCR) assay, targeted to DNA sequences of the Mycobacterium tuberculosis and Mycobacterium avium complexes. All of the twenty five BAL-inoculated rabbits revealed evidence of lobar pneumonia, with thirteen developing lesions of non-caseous granulomatous inflammation, similar to those observed in sarcoidal patients. Microbiological cultivation of lung and alveolar lymph node material, Zihl-Neelsen staining of corresponding tissue sections and PCR analysis of extracted DNA yielded no evidence of mycobacterial infection. Identical processing of biopsies originating from the martyrs, formerly inoculated with drinking water or disinfected BAL, revealed no pathological signs. Our findings suggest that BAL samples from patients with sarcoidosis may carry an agent that produces a disease characterized by similar histological lesions in rabbits. However, culture, and PCR, could not identify this agent as a member of Mycobacterium tuberculosis, or Mycobacterium avium complexes.