The parotid glands and part of the submandibular glands were irradiated in 18 amyotrophic lateral sclerosis patients with very advanced disease and severe drooling problems. In a prospective study, a single dosage of 7.0-7.5 Gy was administered bilateral to the larger part of the parotid glands and the posterior parts of the submandibular glands. Salivary secretion rate was assayed before and after radiotherapy. Sixteen out of eighteen patients reported satisfactory to good reduction in drooling lasting up to 4-6 months, 1/18 developed xerostomia and needed saliva substitutes, and 1/18 reported no effect. Caregivers reported positive effect in all patients. The procedure was well tolerated with few side effects. Low dosage external radiotherapy of the salivary glands is effective in reducing drooling satisfactorily in ALS patients, especially in well-hydrated patients.