In the last decade, a growing number of patients with pneumonia, caused by unusual gram positive rods have been observed. Mostly, the patients had been infected as a consequence of impaired immunity. In some cases, bioterrorist activities may also induce pneumonia by gram positive rods (B. anthracis). In order to bring these organisms to the attention of the medical community, we present three clinical cases and describe six species of gram positive rods, known to provoke this kind of pneumonias. Case 1 was a 84 years old patient with impaired lung function. He was suspicious of tuberculosis (Tbc). Nocardia spec. was isolated. Case 2 was an alcoholic of 46 years with pneumonia. Reactivation of Tbc was suspected. Actinomadura madurae has been isolated. Case 3 was a patient of 58 years with myelodysplastic syndrome (MDS) and pneumonia. N. asteroides was isolated. All patients shared impaired immunity (age, alcoholism, MDS) with impaired lung functions; Tbc had been suspected (Case 1 + 2). Infection by A. madurae was contained by Clindamycin. Therapy of Nocardia with Moxifloxacin (Case 1) or Bactrim (Case 3) was only partly effective. In the appendix, six species of gram positive rods which are known to cause pneumonia, are summarized (Nocardia, Actinomyceta, Actinomadura, Rhodococcus, Corynebacterium and Bacillus).