The suprathreshold olfactory intensity of pure substances can be expressed as a function of three biological parameters characteristic of each substance. These parameters are: the detection threshold, the slope of perceived intensity versus concentration in log. log. coordinates, and a ceiling to this slope of either physical or biological origin. This study represents an attempt at compiling thresholds, intensity slopes and slope limits determined by many authors, and the selection and standardization of these data based on objective criteria. The selected results include 110 slopes, 124 thresholds, 78 biological limits and 110 physical limits.