In 1985 dentists in the Lothian Region of Scotland were questioned about their use of prophylactic antibiotics for patients at risk of developing infective endocarditis. Replies were compared with those obtained from a similar survey in 1981. The results showed a marked change in practice with widespread adoption of the single-dose oral amoxycillin regimen; this was the regimen of choice for 63% of general dental practitioners. For patients allergic to penicillin 76% of practitioners used erythromycin and there was a decline in the use of tetracycline and clindamycin. The adoption of amoxycillin reflects the ease of compliance with a simple single-dose regimen. This change has produced a striking improvement in the timing of prophylactic antibiotic therapy.