Ambulatory diagnosis of sleep-related breathing disorders (SRBD) is necessary due to their high prevalence and to the limited capacities of sleep centers. Categories of SRBD which must be diagnosed and differentiated are defined. Indications for ambulatory diagnosis are given. A selection of systems on the market in Europe are given and described in terms of their parameters. The correct system for diagnosis in a specific patient must be selected according to the specific question. The issue of ambulatory diagnosis of SRBD has gained importance in Germany because beginning in spring 1992 physicians will be reimbursed if they continuously record respiratory signals, heart rate, oxygen saturation and movement in their patients and if they qualify by attending a one-week training course.