Information provided by the three commercial manufacturers of diphtheria and tetanus toxoids and pertussis vaccine, adsorbed (DTP vaccine) indicates a striking increase in the number of lawsuits filed against them alleging damage caused by the vaccine. Only one such case was filed in 1978, whereas 73 were filed in 1984. During the seven-year period from 1978 to 1984, the average amount claimed per suit has risen from $10 million to $46.5 million. If the current trend continues, suits will pose an increasing threat to the availability of DTP vaccines in the United States.