We describe a case of Mycoplasma pneumoniae chest infection associated with Stevens Johnson syndrome. The patient had extensive epidermal bullous vesicles, oropharyngeal and genital ulceration and required prolonged ventilation due to respiratory failure. Mycoplasma pneumoniae infections are often asymptomatic but can involve multiple organ systems. Respiratory tract involvement is generally benign though 3 to 10% of patients develop clinical pneumonia. Secondary skin reactions are common (20 to 25%), although few patients infected develop Stevens Johnson syndrome. It has been suggested that Mycoplasma pneumoniae may be the most common infectious cause of Stevens Johnson syndrome.