Previous studies on Langerhans'-cell histiocytosis (LCH) were mostly retrospective and patients had been recruited over a long time period. The aim of the present study was to establish data on the clinical presentation, diagnosis and treatment of currently affected patients. Data on the clinical history, diagnostic work-up and course of histologically confirmed LCH in 58 adults were obtained with the aid of a questionnaire. A differentiation of the patients (average age 43.5 +/- 7.7 years, 66% women, 34% men) by the various clinical forms, revealed single-organ involvement in 42 of the patients (72 %), and multisystem involvement in the remaining 16 patients (28%). In the 42 patients, who had involvement of a single system, 23 had pulmonary involvement only. Multilocular osseous involvement was observed in 9 patients. In both single-organ or multisystem LCH the most common affected site was pulmonary involvement (62%), followed by osseous (50%) and cutaneous involvement (15%). 51 patients (88%) were smokers or ex-smokers. Dyspnoea (60%) and cough (47%) were the most frequent initial symptoms. In adults with LCH the pulmonary system is most frequently involved, however almost one-third of the patients present with multisystem disease.