The function of the salivary glands, the caries situation, and pathological alterations of the oral mucosa of 32 patients, 20 dentulous and 12 edentulous, who had received long-term treatment (median 5.5 years) with cyclic antidepressant drugs were studied. Anamnestic information on dry mouth problems was recorded. Although a normal secretion rate for stimulated saliva was recorded in about 50% of the patients all but four complained over dry mouth. The majority of the patients had low values of salivary buffer capacity, high numbers of Streptococcus mutans and lactobacilli in the saliva, and poor oral hygiene. All except two patients had received dental care a year or less before the time of examination. Nevertheless 72% of the patients showed pathological alterations of their oral mucosa and 55% of the dentulous patients had new caries lesions. From an evaluation of the caries risk it was concluded that about half of the dentulous patients had a high caries risk, which seemed to be emphasized if combinations of psychotherapeutic drugs were used. It is recommended that patients receiving treatment with antidepressant drugs should be given an individually related dental prophylactic programme.