214 cases of typhoid fever (TF) occurring in Switzerland between January 1980 and December 1984 were analyzed for travel history, vaccine status and nationality. A subgroup of Swiss tourists who acquired TF in India was compared to a sample of healthy Swiss tourists who travelled to India in 1983 to determine the factors predisposing to TF. Eighty cases of TF occurred in Swiss tourists to the Third World, of whom 26 had travelled in India. Among the latter, the length of stay was longer than in the control sample of 258 healthy tourists, and "trekking" (travelling off the usual tourist routes with backpacking) was more frequent. 20 of the 80 patients had been vaccinated with the live oral typhoid vaccine Vivotif (strain S. typhi Ty 21a, contained in gelatine capsules, to be taken with bicarbonate capsules), marketed in Switzerland in 1981-1984. Comparison of the vaccination rates in case and control groups indicated that the vaccine efficacy was not significantly different from 0% during the time of observation. This lack of efficacy may be related to inadequate dosage and to the lack of stability of the vaccine. Forty cases of TF occurred in Swiss who had travelled in European countries, of whom 8 had not travelled outside Switzerland. The remaining 94 cases occurred in non-Swiss travellers, a majority of whom were from Mediterranean countries. TF in Switzerland was associated with a history of travel in 96% of cases. The live oral typhoid vaccine Vivotif was ineffective between 1981 and 1983.