Xerostomia due to chronic graft-versus-host disease (GVHD) or total-body irradiation (TBI) is an important cause of morbidity after BMT. The ophthalmic or oral form of pilocarpine, a parasympathomimetic agent with predominantly muscarinic activity, was given orally to 13 patients with moderate (n = 6) or severe (n = 7) xerostomia due to chronic GVHD (n = 7) or TBI (n = 6). The duration of 19 courses of therapy was 7-245 days (median 73). Ten patients (77%) noticed significant improvement in salivation and relief of symptoms which reached its maximum after 7-186 days (median 46). Difficulty in eating and speaking reduced, and there was a beneficial effect on the oral mucosa and teeth. Xerophthalmia improved in one of six patients. Five patients had adverse reactions; wheezing (n = 1), and increased sweating without (n = 3) or with (n = 1) abdominal cramps (n = 1); leading to discontinuation of pilocarpine in one. Three patients stopped pilocarpine, became symptomatic again, but the benefits were reproducible on restarting pilocarpine. The ophthalmic preparation was as effective as the oral, and was one-tenth the cost of the oral. We conclude that oral pilocarpine is effective in relieving xerostomia associated with chronic GVHD and TBI. The time taken for a response to be seen is variable, and unless significant adverse effects are encountered, pilocarpine should be continued for 6-8 weeks before it is considered to have failed.