The substantial decline in the incidence of syphilis, especially in women, in Western Countries since 1945 has led some to question the desirability of continuing routine antenatal serological screening for syphilis in pregnancy. No routine figures are available in England with regard to the incidence of maternal syphilis. The incidence of syphilis in pregnancy was estimated for 1981 by means of a postal questionnaire sent to all the Special Clinics in England, and the costs and benefits of the screening programme were calculated by means of a computer-aided program which included a sensitivity analysis. Under various assumptions, the total cost savings from discontinuing screening ranged from £170479 to £325493 per annum, with a ‘best estimate’ of £252713. Benefits in terms of cost savings to the N.H.S. resulting from the screening programme ranged from £1870705 to £6975587 per annum, with a ‘best estimate’ of £5121950. When other benefits to society of the programme were considered, total benefits ranged from £3243845 to £14121160 per annum with a ‘best estimate’ of £8322610 per annum. The benefit/cost ratio ranged from 9.20 to 1 to 82.83 to 1 with a ‘best estimate’ of 32.93 to 1. It is concluded that, on economic grounds, there is a strong argument for continuing to screen routinely for syphilis in pregnancy.