The survival in the sigmoidal dose-response curve at given dose can be calculated from a suitable mathematical expression describing the curve. The optimization of the sigmoidal curves to the target models, therefore, was studied under the computer calculation. Using the experimental data of 27 strains of bacilli spores, showing sigmoidal dose-response curves, we can get the most suitable parameters in each model by the programme developed. In finding the least sum of squares of differences between experimental log survival and the calculated log survival of the model at given doses, the most suitable mathematical expression can be obtained. The outline of the programme and the model proposed are also shown.
