Pain and secondary haemorrhage are the commonest complications of adult tonsillectomy, occurring mostly in the community. This is a randomized, double-blind, placebo-controlled, prospective trial of the effect of perioperative amoxycillin on these complications. The incidence and severity of post-operative haemorrhage was measured. For the first 10 post-operative days patients provided a linear pain score, a record of GP visits, and their use of additional antibiotics and analgesics. Of 95 patients considered: 23 suffered a secondary haemorrhage; 54 consulted their general practitioner (GP) because of pain; additional antibiotics were used by at least 31 and additional analgesics by at least 41. No significant differences were demonstrated between the active and placebo groups for any of these measures. This study demonstrates that secondary haemorrhage is common after adult tonsillectomy. Post-operative pain remains a major problem requiring frequent GP consultations. There appears to be no justification for the routine use of perioperative antibiotics.