This chapter presents a case study of a 60-year-old builder who presents with a 12-month history of progressive dyspnoea. Examination of his respiratory system reveals reduced expansion of both lung fields, resonant percussion, and bilateral inspiratory crepitations at both lung bases. Respiratory symptoms of infection with mycoplasma are often preceded by headache and myalgia. Infection with Legionella pneumophila usually begins with a high pyrexia, malaise, and myalgia. Gastrointestinal symptoms are common and may precede respiratory symptoms. The chapter also presents a case study of a 65-year-old female with a long history of atrial fibrillation who presents with a 5-month history of progressive lethargy and shortness of breath. She also has bilateral widespread fine respiratory crackles throughout her lung fields. The lung pathology on exposure to asbestos consists of fibrosis and hence a restrictive defect is to be expected.