sea, vomiting, and cough. Treatment with erythromycin ethylsuccinate had little effect, and the patient's illness pro¬ gressed with development of fever, night sweats, weight loss, and weakness. Two months before admission a chest roentgenogram had shown a left lingular infiltrate that failed to respond to ciprofloxacin. The patient works in an arid portion of the San Fernando Valley, California, and his job includes driving open vehicles in off-road conditions. A few rales at the base ofthe left lung were noted at the time of hospital admission. The white blood cell count was 17 10YL and the hematocrit was 0.25. Results of antibody testing for human immunodeficiency virus were negative. A chest roentgenogram again showed lingular infiltrate of the left lung. A bronchoscopic transbronchial lung biopsy speci¬