This article describes the frequency of mouth care for cancer patients in Belgian hospitals. It also analyses the indicators used for this specific type of compensatory nursing care. The study was designed as a secondary data analysis of the 1990 Belgian Nursing Minimum Data set. The randomised sample included 35,347 oncology patients. Frequency of mouth care was 10.3%. The most important indicators were ventilation (70.58%), nasogastric tube (55.01%), endotracheal tube (43.17%), isolation of the patient (40.57%), malignant neoplasmas of lip, cavity and pharynx (40.21%), age younger than 8 years (37.06%) and disorientation of the patient (31.49%). Frequency of mouth care increased with a higher qualification of staff and higher staffing ratios.