The British Paediatric Surveillance Unit (BPSU) of the Royal College of Paediatrics and Child Health is an 'active' case reporting scheme set up in 1986 to facilitate the investigation of uncommon childhood conditions of public health and clinical importance in the UK and Ireland. Its methodology involves the monthly mailing of a card containing a menu of up to 12 reportable conditions to all clinically active paediatricians in the British Isles. Respondents either indicate any cases seen in the past month or make a nil return. The BPSU forwards details of respondents reporting cases to the investigators, who when obtain information from the clinician. The menu changes from time to time and studies undergo a rigorous selection process. In 1995, the BPSU held an international seminar to review lessons learned during its first decade which would improve and develop surveillance of paediatric disorders. Over the 9 years to mid-1995 a total of 34 studies took place (25 completed, nine still in progress) with a high respondent response rate (e.g. 90% in 1994). Underascertainment had been addressed by seeking, in parallel, other sources of cases, e.g. death registrations, laboratory reports, other relevant clinical specialists, and by use of capture-recapture techniques. Other specialties and countries have since followed the BPSU example providing opportunity for multispeciality and international studies. The latter were valuable, but required careful planning to standardize case definitions and laboratory techniques, otherwise geographical differences in the incidence of study disorders were difficult to interpret. The BPSU has facilitated studies which increased knowledge about a range of disorders and informed national policy decisions. It also increased diagnostic awareness and showed itself able to respond to public health emergencies. Its emulation in further countries will have similar benefits.