The results of a multicentre study of 1668 Spanish prostitutes are described with regard to syphilis infection. For those women who permitted serological tests ( n =1095), 30.59% (confidence interval (CI): 30.55%-30.63%) were positive for markers indicating current or prior infection. After adjustment was made for other variables, a significant association with syphilis infection was observed for periods of exposure (i.e. age and years working as a prostitute). No significant associations were detected for either intravenous drug use, or educational attainment. The results of this study are similar to those of some other investigations into the prevalence of syphilis amongst prostitutes.