Laboratory aspects of a programme of sewer swabbing during and after the Aberdeen typhoid fever outbreak, 1964, have been described. Results were discussed and reasons suggested for the relative insensitivity of methods employed in the isolation of Salmonella typhi. It was tentatively concluded that generalized sewer swabbing in a large city was not likely to be very helpful in tracing undetected excreters of S. typhi during and immediately after a major typhoid fever outbreak. The cost of the laboratory side of this investigation, for staff salaries, equipment, media, etc., was somewhat over £7000.

The authors wish to express thanks to Dr I. A. G. MacQueen, M.O.H., Aberdeen, and his staff including Mr H. B. Parry, Chief Sanitary Inspector and staff, for willing and helpful co-operation throughout this programme. Grateful acknowledgement is also made to Dr B. Moore of the Public Health Laboratory, Exeter; to Dr E. S. Anderson of the Enteric Reference Laboratory, London, for ‘phage typing’ the numerous isolations and to Dr Joan Taylor of the Salmonella Reference Laboratory, London, for assistance in typing Salmonella spp. isolated. Especial thanks are due to our laboratory technicians and other staff for the willing support given during the investigation.